FAQ

Q: My girlfriend/boyfriend refuses to have sex with me?
A: This is common if they are of High Virtue. You must have H in a private place or where no one is around. If someone comes into the area mid-H, they may cancel the H from embarassement.
Q: My partner has ended the sex scene after switching to another position?
A: If your partner has High Virtue, they may not want their first time right away. You may need to make them orgasm or raise sexual compatibility (possibly both) before they will let you switch to that position.
Q: How do I end a sex scene? I can't click the button?
A: The button becomes available after your partner has finished her/his orgasm.

Basic Requirements for H

This lists the requirements for getting sex in ascending order according to virtue. The higher the virtue, the more requirements must be met.

Like/Love: The most basic of requirements, and a prerequisite for all others listed. Any character would have to like yours in order to consider any physical contact. The lower virtue would consider it if Like is high enough, the higher the virtue, the more Love is required.
Lust: Get the character horny: especially necessary if it's the first time having sex with the character. Talk Lewd, Kiss, or Touch can do this, as can witnessing other characters engaged in sex.
Physical contact: Low virtue characters would agree to sex without at least a kiss, and may not accept a kiss without a hug, or a hug without a head pat. The lowest virtue may respond well to a grope without a kiss if Like or Love are high enough.
Lovers: This is necessary with High virtue characters. Even at Low/Lowest virtue, a character is more wiling to have sex if you're in a relationship, even when love has declined.
Invite to Private Space: High and Highest virtue characters in particular don't want to have sex in public. You will need to invite them to private spaces, such as the Love Hotel or your bedroom, in order to initiate H.

Exceptions:

Blackmailing: Any character that has been successfully blackmailed can always be forced to H.