On the way to hospital to visit his father, art student Ayuta Ipponyari (Hayato Ichihara) spots and falls in love with a beautiful woman on the train. He hurriedly draws a sketch of her until she departs the train.
At hospital Ayuta is talking with his father when a new doctor enters the room and introduces herself as Dr. Haruhi Godo (Manami Konishi). Ayuta immediately recognises her as the beautiful woman from the train. He also learns that she's divorced and an older sister of his long-time girlfriend Natsuki Saito (Erika Sawajiri), who wants to be his bride.
Believing Haruhi is the One, Ayuta attempts to woo her into accepting his romantic interest, not realising that their emerging love triangle would carry lasting consequences for all involved.