I don't recall anything except the maid service events on the weekend at the cafe, and I can't remember if there's any actual sex even then.
There are some hints at the hospital, school, and police station of orgies, but the only events to my knowledge that are actually shown are the scene with the 4 teachers on Mr. Simpson and Alice at the C-Mart. (Alice has a sign saying basically "feel me".) Neither has actual sex with other guys, but it is implied.
Update: Since I posted this, I've gotten scenes at the school and bus station where corrupted chicks are talking about seducing other men, but so far, the only instance that you see actually can see seems to be Mr. Simpson & the teachers. There are several places where other guys are watching girls stripping, masturbating or having sex with you, but so far none have gotten involved directly.
I should mention a special case. The mayor is apparently having an affair with his secretary and you catch them in an embrace but, again, no actual sex is shown. This apparently is independent of your storyline and does not involve the potion.