
This page shows the guy with his arm around him, then him in bed with someone else while crying and looking at his phone, and he said he couldnt give him up, so it seems he did sleep with him but maybe only once http://www.mangago.zone/read-manga/oko_sama_box/mi/0a09806df74791cdd3f925457fd072d6_chapter-5/19/

I doubt that Fujita slept with the guy. The image of him crying in bed just looks like the blanket is pushed up behind him. I feel the mangaka would have made it much more obvious if that scene was indeed showing Fujita with that man. I think that guy was just introduced to cause the misunderstanding, and I believe Fujita when he tells Kawasaki that it's not what it looks like. Fujita's been stalking Kawasaki since HS ended so I doubt he was interested in other guys (similar to how Kawasaki isn't even interested in porn).

Maybe his ex boyfriend, as an replacement for Kawasaki ?but fujita said to kawasaki that" that's not what you think" when they saw by kawasaki in the street but fujita didn't have a chance to explained that's why I'm still confuse about that guy

I think that guy was his ex bf and having sex while calling the name of Kawasaki that's what I think about the picture, to forget about Kawasaki but he still love Kawasaki and then they ended up in broke up, maybe that's what I thought

I won't say he never tried, but I just can't see when or how. He was totally obsessed with Kawasaki. All of his choices were based on that obsession, so I don't think he's even thought about sleeping with anyone else. When would he have the time to even nurse that kind of relationship? When he wasn't working, it seemed like he was hanging around the area. Maybe the guy that grabbed him on the street found out about him stalking Kawasaki, and wanted him to stop? His parting statement to Fujita just didn't seem like one that a previous lover would say.
Who was the guy that Fujita was struggling with in the streets at the end of Chapter 3??? Did Fujita sleep with him before he met Kawasaki again???
Pleaseeeee somebody explain it to me. Am I missing something? It's been bothering me since forever!(╯°Д °)╯╧╧