Boku wa Imōto ni Koi o Suru

Plot

Yori and Iku Yuki are twin brother and sister, who have been extremely close since they were born. During their childhood, Yori used to tell their parents that he would marry Iku. While their parents brushed this off as an innocent childhood fantasy, Yori knew that his feelings were more than an innocent crush on his sister. When they are fifteen, his feelings have grown stronger than before. Yori has by now understood that he has fallen deeply and hopelessly in love with Iku, which makes him feel ashamed. Due to that they share a bedroom, Yori finds it harder and harder to resist his feelings for her, so he begins to distance himself from her and acts coldly to her. Iku is hurt and shaken by his harsh treatment towards her, but she tries to remain cheerful and make him smile. One day during school, Yori gets into a fight after a classmate makes fun of Iku, and gets injured. Tomoka Kusunoki, Iku's best friend, tends to his injury and tries to comfort him. In midst of this, she suddenly kisses him and professes her love to him. When she asks him if she is good enough for him, he sees this as an opportunity to surpass his feelings for Iku. He proceeds to kiss her and has sexual intercourse with her at a hotel. This encounter, however, does nothing to help him forget his lust for Iku. Tomoka mistakenly thinks that Yori reciprocates her feelings and calls him her boyfriend. Yori, however, decides to hide this from Iku so she won't get upset. He later tries a new strategy: go to an out-of-town high school. Days later, Yori and Iku get into a fight after Iku talks about her dreams of having a boyfriend and going on dates. Yori gets really mad about this and yells at Iku to shut up. Iku does but starts crying. While she is crying, he kisses her, which shocks her, and he confesses his love to her. Iku is taken aback by his confession and rejects his advances because he is her brother. However, she sees the sadness on his face and realizes that, while she is uncertain if she loves him more than a brother, she may lose him by rejecting him. She kisses him and feels uncomfortable by it, which Yori notices and tells her to wait until she is sure of her love for him. Over the next several days, they try to begin an intimate relationship, with Iku slowly growing adjusted to Yori's advances, and keeping their parents in the dark. Haruka Yano, Yori's best friend, immediately notices the twins' closeness but doesn't tell them. Iku continued to be torn between her guilt of committing incest and her desire to remain together with Yori. Her guilt, however, completely disappears when she discovers that Yori is planning to enroll in a different high school and that he has been seeing Tomoka. She tries to have sex with Yori, but in the process, he rejects her because she still doesn't love him yet. The next day, as she sees Tomoka clinging to Yori, Iku realizes that she has finally fallen in love with Yori. After confessing to him, they skip school and flee to a church, where they remember playing at when they were little. They try to have sex in the church, but Iku tells him to stop because she feels that God is watching them. Yori agrees and decide to go home.

Soon after, during school, Tomoka talks with Iku and their friends about her first time with Yori, which angers Iku. Yori comes in and tells Tomoka that their relationship is over before leaving with Iku. Tomoka smiles while crying and doesn't understand why he broke up with her so suddenly. When someone mentions that Yori probably has someone else he likes, she quickly realizes that that person is Iku. Iku fights with Yori over his indiscretion with Tomoka. He hugs her as she tries to get away from him, but when she sees him cry, she gives into her feelings and hugs him back. Later that day, Iku has Yori meet up with her and tells him that she wants to make love to him right now, which shocks but pleases him. They go to a hotel, and after Iku is initially apprehensive, they finally have sex for the first time. Yori is thrilled that Iku is his, but feels guilty for making her cross the taboo line and asks for God to punish only him. Days later, they graduate from junior high school and Iku realizes that Yori still plans to leave for a different high school. Yori tells Yano the truth of his relationship with Iku, which Yano knew but he asks why is he still leaving. Yori says that he is torn between his desire to protect this relationship and wanting to destroy the sin of it. Yori tries to comfort Iku, who asks why he wants to go. Yori says he doesn't want to leave, but if he stays, they can't be a normal couple. However, if they were another city, where no one knows them, they could be a couple. Iku reluctantly agrees to let him go, with the promise that they will stay in touch.

Yori arrives at his high school, and to his horror, he finds that Tomoka has enrolled in the same school. She tries to get him to take her back, but he rejects her, which doesn't seem to bother her. For their sixteenth birthday, Yori and Iku receive cell phones, which makes easier for them to stay in contact. Iku visits with Yori as much as possible because Yori is allowed limited visits outside of the school. He befriends Takuma Kakinouchi and his girlfriend Mayu Taneda, who act his confidants. For his birthday present to her, Yori gives Iku a diamond clover ring as a promise of eternal love. Separated from Yori for weeks at a time, Iku is placed in the care of Yano, who acts as her protector. Yano helps the twins see each other at school and even arranges them to spend the night together. When he tells Iku that he knows about the relationship, he assures her that he will keep it a secret. However, as he spends time with her, Yano slowly falls in love with Iku. Yori vows that he will never give Iku up, and the two best friends have a friendly rivalry over Iku, who is oblivious to Yano's feelings. The twins' parents mistake Yano as Iku's boyfriend and take an instant liking to him, but he says that they are not a couple. When he does tell Iku that he likes her, Iku rejects him because she loves Yori.

Yori soon realizes that Tomoka is determined to get revenge against him and Iku for breaking up with her. She has them be caught in Yori's room by fellow students several times in order to expel him (girls are forbidden to be in boys' dorms). When Yori gets light punishments for the offenses, she takes a cell phone picture of the two kissing and threatens to send it to everyone they know if he doesn't sleep with her. When he appears to accept the deal, he deletes the picture and tells her to leave him and Iku alone. Tomoka, however, refuses to listen and continues with her plan to expel him. Some time later, while Yano is at Iku's house, her father comes home and happily tells his wife that he ran into their longtime friend, Dr. Yuugo Mori, which takes her aback. He tells her that Yuugo has a daughter who is the same age as Yori and Iku, and promised to have Yori engaged to the girl. The twins' mother refuses this and asks about when he said the girl is similar to Yori. This sounds suspicious to Yano, who tells Yori that he thinks Iku might not be his sister. Yori rejects this possibility, even though he later finds out that he and Iku have different birthdays. When Iku sneaks into the school to visit Yori, Tomoka hires a group of classmates to rape Iku. Fortunately, Yori catches them and punishes them and Tomoka. The school principal decides to expel Yori for continuing to let Iku into his dorm. Iku is happy of the news, which annoys Tomoka and calls her stupid. Yori defends Iku from Tomoka's insult, and she threatens to tell his mother about the incestuous relationship. He doesn't believe her, but the twins find that their mother has overheard the conversation. Again, Yano lies, saying that Tomoka was joking and Iku is his girlfriend. Their mother does not believe them, but doesn't say it out of fear, and takes the twins home. Yori enrolls into Iku's high school, where they meet Yuugo's daughter Azusa. She notices that Yori and Iku don't resemble each other while she looks just like Yori. This makes Yori consider the possibility that Iku may not be his sister after all. Azusa tells her father of how different the twins are, and after he invites the Yuki family over to his house and he sees Yori for the first time, he confronts their mother. Yori witnesses an intimate moment between the two and suspects that they may have had an affair. He later finds Iku's unfilled birth certificate and photographs of his parents with Yuugo. He is convinced more than before that Iku may not be his sister and that the man he believed to be his father is not. Azusa confesses to Yori that she believes they are half-siblings, and then Yuugo confesses that he has been in love with Yori's mother since college and he believes that he is Yori's biological father. He secretly uses a piece of Yori's hair to do a DNA test, which confirms his suspicions. He tells the twins' mother of the news and is shocked when she admits she knew Yori is his son. She had kept it a secret out of fear of ruining her family. Yori confides in Yano about whether or not Iku is his sister, and Yano talks to a family friend, who says that the unfilled birth certificate could indicate Iku was abandoned as an infant and then adopted by their parents. Yori is sad and yet happy that he and Iku will be able to live as a normal couple in public. After this, Yori makes his feelings for Iku clear to his mother, who reacts in shock. She tells Yori to stay away from Iku because they are siblings. Yori doesn't believe her and threatens to destroy the family if she tells anyone about the relationship. With his mother horrified, he takes Iku to their room. As they are making love, their mother confronts them and tells them that they are siblings, but Yori asks her to answer his question about Iku's birth certificate. She tells the twins and their father that they are twins, but half-twins; they are the result of heteropaternal superfecundation. She tells them that Yori is her son with Yuugo Mori and Iku is her daughter by her husband. Sixteen years ago, when she was about to marry her husband, Yuugo confessed his love to her, and although she had feelings for him, she refused him. At that moment, he kissed her and both had sex. She tried to forget about the betrayal and slept with her husband, in the same day. Three months later, she found out she was pregnant with twins and was unsure who the father was, until the twins were born and saw the physical difference between them. She becomes physically ill after telling the story and lashes out at Yori for his incest with Iku.

Realizing that they may be separated now that their parents know their secret, Yori and Iku run away from home with Yano's help and stay at his beach cottage. Yori tells Iku that if they had a child together, their parents will never have to separate them. Iku is hesitant at this idea, but agrees, and they make love in an attempt to conceive. Later on, they go to a church to pray, and Yori realizes Iku cannot give up their parents just to be with him. He also realizes that they have nearly destroyed their family and Yori blames himself for dragging Iku to commit incest. They decide to return home and reconcile with their parents. Yori decides to leave the family and go somewhere he can never be found in hopes that his and Iku's feelings will disappear overtime. Before departing, he cuts Iku's hair (with Iku's permission) from what it looked like from her childhood at her request, and he slips out when she falls asleep. When she wakes up and finds him gone, Iku falls into a deep depression. However, she soon realizes that she never did anything for Yori and resolves to find him no matter how long it takes. Over the next ten years, Iku manages to get into a university and becomes a sales representative for Yano's company. Yano has frequently asked Iku to marry him, but she rejects him. During a trip to England, she goes to a library because she thinks it would be a place Yori would go to. They finally pass each other, but don't recognize the other until after a few seconds, and turn around and embrace. In the climax, Yori states that he is still in love with Iku.

Characters

Manga

Written and illustrated by Kotomi Aoki, Boku wa Imōto ni Koi o Suru were originally serialized in Japan in Shōjo Comic. The individual chapters were collected and published in ten tankōbon volumes by Shogakukan, with the first volume released May 26, 2003; the last volume was published on August 26, 2008. The series is licensed for regional language releases in France by Soleil Productions under the English title Secret Sweetheart, in Spain by Editorial Ivrea, and in Taiwan by Ever Glory Publishing. The original volumes were also imported to the United States and sold as is by Borders and Waldenbooks bookstores in early 2005. In March 2008, to celebrate its 40th anniversary, Shōjo Comic posted free chapters of Boku wa Imōto ni Koi o Suru on its website, along with a new side-story.

A spin-off series, Boku no Hatsukoi o Kimi ni Sasagu (僕の初恋をキミに捧ぐ, lit. "I Offer You My First Love"), began serialization in Shōjo Comic simultaneously in 2005. Focusing on Yori's upperclassmen Takuma Kakinouchi and his childhood sweetheart Mayu Taneda, the series ran until mid-2008. Shogakukan published the individual chapters across twelve tankōbon volumes, with the first released December 20, 2005 and the last on August 26, 2008.

Original video animation

Boku wa Imōto ni Koi o Suru: Secret Sweethearts – Kono Koi wa Himitsu (僕は妹に恋をする シークレット・スウィートハート この恋はひみつ, lit. "I'm in Love with my Little Sister: Secret Sweethearts – This Love is a Secret") is the original video animation (OVA) adaptation of the manga. On May 18, 2005, Shogakukan released a DVD for the original video animation. Directed by Mayumi Nishimoto, the hour-long, one episode OVA used the song "Ai ga Hoshii" (愛が欲しい, lit. "Desired Love") by Shion as its ending theme.

Live action film

The manga was adapted into a live action film by Toshiba Entertainment. The film was directed by Hiroshi Ando and produced by Shogakukan, Toshiba Entertainment, Zoom Enterprise and Nippon Television. It was released in Japan on January 20, 2007 and in Taiwan on June 1, 2007. The film features Jun Matsumoto as Yori Yuuki, Nana Eikura as Iku Yuuki, Ayaka Komatsu as Tomoka Kusunoki, Yuko Asano as Saki Yuuki and Yūta Hiraoka as Haruka Yano. The ending theme of the movie is "Kitto Eien ni" by Crystal Kay.

The spin-off series Boku no Hatsukoi o Kimi ni Sasagu was adapted into a film entitled I Give My First Love to You. The film was directed Takehiko Shinjo and was released on October 24, 2009 in Japan. The story revolves around Takuma Kakinouchi, played by Masaki Okada, a boy who is told he will die before he is 20, and Mayu Taneda, played by Mao Inoue, the girl who is in love with him.

Reception

The first seven tankōbon volumes of Boku wa Imōto ni Koi o Suru sold 2.5 million copies by May 2006.

A reviewer for Manga News describes the first volume of the manga as "a mature shojo, appealing and rather captivating". A review of the second volume of the manga commends the author's art as "very pretty". It also comments on the incestuous relationship "Between those two brother and sister are sometimes pushed a bit too far and I found Yuki a bit too silly at times. But that also gives charm to the character." PlaneteBD's Faustine Lillaz comments on the manga's art which "barely save the day. The trait is fine and the style rather pure and the background details are rarely presents and when they are it's only to reinforce the forbidden aspect of Iku and Yori relationship (church, bedroom with parents outside)." Carlos Ross of T.H.E.M. Anime Reviews criticized the hour length of the OVA, feeling its compression of the original manga story causing Yori's feelings for his sister to seem "extremely abrupt and out of left field". Noting that the OVA adaptation departed from the usual "incest-taboo" set up, Ross considered the premise "Freudian" and "very unrealistic." Though he found the animation itself average, Ross praised the background art as varying "from gorgeous to amazing". Anime News Network's Carlo Santos criticises the manga for its lack of depth.

"[Yori and Iku] basically spend each chapter getting dangerously close with each other, often in explicit ways, and this smut is repeated over and over until you just want to read some conservative, pedantic pre-Tezuka shōjo manga about how little Chieko became a good obedient wife and waits every day to serve dinner to her salaryman husband because he gets so tired from perpetuating the Japanese economic miracle." – Carlo Santos, Anime News Network

Boku no Hatsukoi o Kimi ni Sasagu received the Shogakukan Manga Award for shōjo manga in 2008. The seventh volume of Boku no Hatsukoi o Kimi ni Sasagu was ranked 5th on the Tohan charts between April 25 and May 1, 2007. The eighth volume was ranked 5th on the Tohan charts between July 24 to 30, 2007. The ninth volume was ranked 3rd on the Tohan charts between October 30 and November 5, 2007. The tenth volume was ranked 5th on the Tohan charts between January 22 to 28, 2008 and 1st between January 29 and February 4, 2008. The eleventh volume was ranked 5th on the Tohan charts between April 22 to 28, 2008 and 4th between April 29 and March 5, 2008. The twelve volume was ranked 4th on the Tohan charts between August 26 and September 1, 2008.