Mutsuo came from a family of farmers. He was a classmate of
Tsuyoshi Nagabuchi at junior high school. Wakashimazu wrestled for
Futagoyama stable, joining in March 1975. Unlike most professional sumo wrestlers, he did not join from junior high school but instead joined after completing high school. He was a high school sumo champion but needed some persuasion from his stablemaster that he would be able to put on enough weight to succeed in professional sumo. He made his debut alongside future top division regulars
Daijuyama and
Kirishima. He reached the salaried
sekitori ranks in March 1980 upon promotion to the
jūryō division and reached the top
makuuchi division in January 1981. He scored 10 wins in his
makuuchi debut. He moved quickly through the division, winning five
special prizes, two for Fighting Spirit and three for Technique. He reached sumo's second highest rank of
ōzeki in January 1983 after two runner-up performances and 34 wins out of 45 in the three preceding tournaments. After a 10–5 in his
ōzeki debut, he broke his leg in the following tournament, but made a remarkably quick recovery, with a 13–2 score and runner-up honours in the next tournament in May 1983. He was popular with the crowds and his lean and swarthy appearance led to him being nicknamed the "Black Panther", His best year was in 1984, when he took two top division tournament championships in March and July, the second with a perfect 15–0 record, but he could manage only third place in the September 1984 tournament and missed out on promotion to the highest rank of
yokozuna. Nevertheless he finished 1984 with 71 wins out of a possible 90, more than any other wrestler (the three
yokozuna at the time,
Kitanoumi,
Chiyonofuji and
Takanosato were all restricted by injury during the year). March 1985 saw his sixth and final runner-up performance. From November 1985 his results started to decline, and in an attempt to change his luck he switched from his trademark
kelly green mawashi to a light blue one, but soon switched back when results did not improve. He retired in July 1987 at the age of thirty, leaving the Futagoyama stable without anyone in the ''
san'yaku'' ranks for the first time in over fifteen years. ==Retirement from sumo==