Wew cheating uke?! I used to read mangas with the same plot like that, it depends on mangakas themselves, well for meh, cheating is possible in relationship, but it always depends on couple to manage themself and fight for their love, btw the second story I was mind blown, I was thinking that spirit would fuck up lil bro's spirit but turns out... They both fucked each other lol
Mayou Otoko