Oniisan to Yobinasai
Complete | Matsuda Usachiko | 2000 released
The old dude (40 y.o. but looks like 20) took advantage of a teenager who is attempting suicide. It even tried to make light of the pedophilia and rape by showing that the old dude symphatizes with the teenager due to their similar situations and former suicide attempt.
I'll Be Gay! Body Switcharoo