You, a man with a criminal record, are met by guidance teacher Popuri Shiodome at a certain school.
Your penance is community service.
If you fail in this duty you will be sentenced to death.
Will you assist guidance teacher properly?
The question becomes, what sort of lessons will you be assisting?
Shiodome sensei is the beautiful teacher of Sexual Education, level 2.
You will be "Sex Oniisan", demonstrating things to the students.
Heh heh heh. That's right. You'll be having sex in front of everyone.