get the cum tank outfit then explore the streets. The game will tell you that you had obtained a vial of cum after having sex with someone on the streets. You need 3 vials of cum for the option to appear
the cum lover's club? You probably need to complete dungeon 2 and then talk to Freya. Talking to Freya is not relevant to this side quest, but it unlocks all the sidequests you are supposed to unlock after this dungeon.
Here's a full guide https://itch.io/post/8052221