The missing teacher, Masahiro Tanba, is found in the toilet, apparently drowned. Makoto Kyogoku becomes the prime suspect as the culprit is likely to have carried the victim to the toilet after drowning him.

Sonoko has decided to introduce Makoto to her parents. But while her father wholly approves of Makoto, especially as he is a fan of martial arts competitions himself, her mother in turn is strictly against a union between her younger daughter, as the prospective heir of the Suzuki Corporation, and an (in her eyes) uneducated, fight-obsessed never-do-wel.