1-2+6 Naoto is found out for selling fake antiques for high prices, by his highschool classmate, Minato. Minato demands that he make up for his actions, and asks for Naoto's body as payment. (And Minato has been in love with Naoto for a decade, and Naoto MIGHT be a jealous dumbass)
3-5 Yamato works at his grandmothers onsen, and meets a painter boy from next door who begs for Yamato to be his muse (and subsequently becomes his boyfriend)
Kouzuka Kottouya no Akujiki