I hope the story doesn't get sidetracked all too often with the MC having a heart on for redheads. I am sucker for short haired hotties so the gf is already #1 in my book. Would love to see a bit light cheating though, especially if the MC is whoring around too. A bit of jealousy never hurts.
Actually I can't remember having seen a story where both MCs are edging themselves on with the partners they sleep with. MC is already on board and wants to see his gf having fun with others, why not have her enjoy him doing other women? They could make a dare out of it, that ulitmatively leads them to having sex with old guy and fat shop owner