What was the point of the black haired guy at the end of chapter 2?

He's the fanboy from the later chapters. It's also heavily implied he was the guy that Ikumi did a porno with as Kai. The guy that quit after one time. So they were like kindred spirits. That guy went a different route while Ikumi seemed to stay more true to himself.

No he's just a fanboy, he never did anything with him but recognized him from his videos.

He was a porno actor at one point.