The SF club is a school club, deliberately abbreviated "SF", but actually it means "sex-freinds". It's a place where people can have sex with anyone just for pleasure.
The rules are
- keep the club activities secret, unless informing someone trusted to join,
- anyone left over (not having sex) films everyone else having sex, the footage is only freely viewable to everyone in the club, no-one else.
The known members are
- Alice Asagiri ("president")
- Kaori Yumeno
- Yukiteru Tamaki (absorbed in by his own weakness)
- Reona Haume
- Aruto Usui
- Shion Nabatame
- Seles Miyuki
- Ayame Meiku
although other unnamed characters are shown to have come and gone.