Searching for a cheating uke (6 posts, 7009 views) Posted: 1997d 22h, 8m ago by pookaloo in Yaoi/Yuri
It's been a while but I believe Rules and its side stories + prequels have a lot of cheating involved between the couples.
Also, definitely read Double Call. It has all the stuff you're looking for.
EDIT: BTW the cheating is only part of an arc and won't c ...