She was volume 4. A yuki onna who's species feed of male vitality (general energy, not the succubus kind of vitality) but she prefers to do it during sex to give something back to the male. She has an enormous appetite that drove away all the boys until the MC and his isekai cheat skill that gives unlimited vitality came along. He refused to sleep with someone he didn't know but offered her food anyway. For being a nice guy and an unlimited buffet, she fell for him.
Personally feel part 2 should focus on the 3 boys developing relationships with their love interest (the harem for Touma) while Ice sending more actual enemy they turn into allies but not part of the main party but i'm not the author so hopefully he surprise us with more interesting story revolving around the party dynamics
For all of the hareming and seduction attempts, it is interesting that not only is Ice still the only one that has actually shown herself naked to Touma, she was perfectly comfortable with it.
It is really refreshing and honestly why I like this so much. They are goofballs, but they are good goofballs. Not a fan of their fetishes, but their love interests are definitely compatible.
The most likely ones should either be Maria or Ice but then again, after the Quintuplets I don't even try anymore.
Sofia (second) best girl tho. After Athenes who unlocks all the other routes as well.