He entered Tenri University in 1978,[1] and continued his success by winning the college-level world judo championship in 1979 and 1980.

After graduating from Tenri University, he began work as a teacher for a school in Nara Prefecture in 1982.

He was chosen as the -60 kg representative for the Japanese olympic judo team for the 1984 Summer Olympics, where he won a gold medal by defeating future gold medalist Kim Jae-Yup only 69 seconds into the match.

[1] He also won a gold medal at the 1985 World Judo Championships, but retired to concentrate on his work as a teacher.

[2] Hosokawa has served as an instructor for the Japanese Olympic Committee since April, 1997, where he coached many lightweight judoka, most notably 3-time gold medalist Tadahiro Nomura, whose father was Hosokawa's coach during high school.