In a Japanese school, 5 adolescent geeks join the new sport teacher and take up the challenge to take part in the synchronised swimming competition, in-spite of the mockeries of the real sportsmen.

Drawn by the exorbitantly high hourly wage of 112,000 Japanese yen, ten men and women gather at a mansion. Everyone thinks the simple psychology experiment will get them some quick cash... until one of them winds up dead. The participants are overcome with frenzied suspicion. Various deadly weapons are left in their rooms and they are killed off one by one.

Toru Kojima and his friend Koji are young student boys with one thing in common — they both love to date older women. Koji is a playboy with several women, young and older, whereas Toru is a romantic with his heart set on on certain lady.

一天夜里，一名男子在东京郊区被车撞死。死者的妻子法子是一个爱出风头生活奢华的女人，暗地里还有一个情人。警方通过调查发现，死者的死因很可疑，而法子是三亿意外死亡保险金的受益人，存在着充分的杀人动机。然而，法子却拥有完美的不在场证明。案情陷入了僵局……