let me explain the whole story

.
.
.
.
.
.
.
.
.
.

Woah that was one hell of a manga so people who are confused let me explain this .So Kouta is a pervert who loves to have public sex and Sei is his friend with benifits turns out the neighbour guy who seemed like was trying to patch them up is a huge stalker of Kouta and later it is reavealed that Kouta knew he was being stalked and he loved that so he set up a camera for that stalker.He got fun from it lol .In his flashback it is seen that his dad who always compared him too his big brother was in a sexual reletionship with his own child and he became really jealous of the fact that they were fucking lol .So when he became friends with Sei he thought that to make him stay by his side he needs to have sex with him.Later it's shown that Kouta's brother meets the stalker which is arranged by Seii. IT meant Sei was a friend of Kouta's brother and knew everything about him from the start .ok so I hope this helped ╮(￣▽￣)╭ I am on laptop so I did not have any problem with the pic quality thank u I totally loved this manga specially the plot twists (๑•ㅂ•)و✧