He was born in the Philippines to a Japanese father and a Filipino mother. His family moved to Japan when he was about one month old. His parents had always been fans of sumo and from a very young age he had aspired to be a sumo wrestler. He was a member of the sumo club at his primary school, and when his junior high school did not have a sumo club he decided to attend practice at an area high school and other locations so he could continue doing sumo. He participated and did very well in children's sumo and also in national amateur sumo tournaments. However, in his third year of junior high school his parents divorced and he moved back with his mother to her native Philippines. He graduated from junior high school there and in May 2006 returned to Japan. Still interested in sumo, he decided to join Chiganoura stable.
He first stepped on the pro sumo dohyō in July 2006. Being a diligent trainer, and managing to avoid injury, he rose through the ranks and in a little over a year and half achieved his first championship at the rank of sandanme 46 with a 7-0 perfect record. It would take him another two and half years of mostly winning records to reach the second division jūryō in November 2010. He entered jūryō at the same time as Takayasu. Both had the distinction of being half Filipino as well as simultaneously being the first two wrestlers to enter jūryō that were born in the Heisei Era.
Masunoyama only managed a 6-9 score in his first jūryō tournament but as he had debuted at the relatively high rank of jūryō 11, he was spared relegation. In the January 2011 tournament, he won his first five bouts in a row, but on the sixth day in morning practice he injured a ligament in his right leg. He made the decision to continue competing, and managed to beat Kakizoe on that day. However, two days later he aggravated the injury in a bout against Daidō and was obliged to miss the next day and take a fusenpai. He then returned for two more days, both wins against veteran wrestlers Tamanoshima and Chiyohakuhō before losing again and re-aggravating his injury to miss the final two days. Through all this he still managed an 8-5 record with two absences. Three tournaments later (with one being missed due to the sumo match-fixing scandal), at the rank of jūryō 1 he came just short of a championship, but lost in a playoff to Myōgiryū who was in his jūryō debut. This record allowed Masunoyama to be promoted to the top-tier makuuchi for the following September tournament.
On the fourth day of his makuuchi debut in a bout against Tochinowaka Masunoyama injured the same ligament in his left leg that he had previously injured in his right leg. He was forced to bow out of the tournament with only a 2-3 record, and was demoted back to jūryō. Though advised by his doctor not to enter the next tournament in order to let his injury heal, he insisted on fighting on. However, unable to do much training and hobbled by his injury he had losing records in the following two tournaments. He returned to form in the next tournament in March 2012 and posted strong winning records in this and the following tournament. He re-entered makuuchi in July 2012, marking it with an 11-4 win and the Fighting Spirit prize. However he had two losing records to only one winning one for the remainder of the year. In 2013, he had a lackluster performance, recording mostly losing tournaments, but mostly records of 7-8 which kept him from falling too far down the ranks. This continued in 2014, and his unimpressive 4-11 score at maegashira 13 led to his relegation to the jūryō division in July.
His downward slide continued in 2015 and absence from the dohyō meant he had fallen to the bottom of the makushita division by September. After having surgery on his right knee for a dislocation and meniscus damage, he declared that he would enter the March 2016 tournament after a five basho absence. He was ranked in the jonidan division for this tournament and came through with a 6–1 record. He was promoted to the sandanme division for May 2016 but withdrew from that tournament after losing his first match. He sat out the July tournament with injury and was therefore demoted to jonokuchi, the lowest division. He is only the second wrestler with top division experience to fall to jonokuchi since the beginning of the Showa era – the other being Ryūhō in 2012. Finally back on the active list for the September 2016 tournament, easily took a 7-0 perfect record and the jonokuchi championship and secured a second successive promotion with a 6-1 in jonidan in November. He missed the January and March 2017 tournaments through injury, but entered the May tournament on Day 7 at jonidan 81 and secured a 4-0-3 winning record. In July he won all seven of his matches in the jonidan division, although he was defeated in a playoff for the championship.
In July 2006, Masunoyama was the sole new recruit into professional sumo, and this garnered him a lot of attention with the press. The press has continued to be enamored with him because of his friendly character, diligence, and ability to cope with adversity. He has also appeared on various television programs to be interviewed and has proven himself to have a remarkable singing voice on these programs.
He has said in interviews that he feels indebted to his mother for raising him on her own, and he sends money to her in the Philippines. He expressed hope to one day buy her a house.
Earlier in his sumo career, Masunoyama had initially been advised by a doctor that he had heart disease and should be careful not to overstrain himself; this also appeared to reflect in his sumo, where after an initial spurt of energy at the tachi-ai he would collapse after around 20 seconds from exhaustion. Eventually however, the coach at his stable insisted on a second opinion and a thorough heart examination was conducted which found no evidence of a heart condition.
Masunoyama goes on the offensive right from the tachi–ai or initial charge, using pushing and thrusting techniques (tsuki/oshi). Nearly half of all his victories are by either yorikiri, the force out, or oshi dashi, the push out.