Consensual Sex
Obviously you're going to have to work your way into their hearts, this can be done by either giving them gifts or have them participate in battle with you for a while. Careful though, trying to get to have sex with you too early will lower their affinity towards you making the process longer
Bathing
The protagonist can watch and join girls in the bath
Gravure
Certain NPCs will allow some girls to pose for photographs to earn cash
Groping
The protagonist can grope girls in certain areas, while they sleep, and anytime while they're enslaved.
Rape
By the protagonist (He's usually only able to do this while the girls are sleeping or by defeating them in battle, the later of which leads to enslavement), and by certain enemies when you lose to them
NTR?
Most of the girls you find can end up being the protagonist's girlfriend, I guess you can consider them being raped after being defeated in battle as NTR
Enslavement
You have the choice of enslaving all the girls you come across (Except for one as she's automatically your slave when you get her) when you choose to attack and rape them while they're following you in town
Exhibition
Can only be done with enslaved girls as far as I know, certain NPCs will appear in town if you have the girls walk around naked
Peeping
You are able to watch girls change their clothes, bathe, and use the bathroom
Watersports
There are a lot of this in this game, you can either peek in on them or have enslaved girls pee where you stand
Breast Expansion
This can happen by giving them a drug, by certain enemies, or a certain area
Milking
This is mostly used to breastfeed the children born from the girls to improve their stats
Pregnancy
All the girls can be impregnated by the protagonist or certain enemies during certain days
Prostitution
Enslaved girls can be prostituted for cash
Bestiality
Girls can be raped and impregnated by some animals
BDSM
This can only be done to enslaved girls (You need to create the bar dungeon first)