The black haired guy (Shimojou) is a "lowlife" whos life is booring. That is also why he does what he does. He is gay and often thinks about his highschool life, when he met that blond guy. He secretely fell in love with him but never admited it (in the past).
When they were in Highschool the blonde guy disapperead. Shinoujo did try to find him, but it was hopeless. He is still waiting for the other one to find him ( = come back to him) since he always found his hideout when they where in highschool.
The blond guy in the present is a undercover cop. He is investigating Shimojou.
I hope I could explain well.

Can someone summarize what just happened. This chapter was so confusing, I still couldn't get it after rereading it. Nothing I read in this chapter was understandable, so plz be detailed.