I regret not immediately commenting my thoughts on this after reading this.
I read this 3 days ago and I gotta say it was a good experience from what I remember, the writing was really good, I feel like I could somehow relate or more like understand the characters and their motives.
It was kinda satisfying to see the situation go full circle
From them during highschool
Matsuda hating on Kamiko
Kamiko being curious about Matsuda
And Matsuda's crush in the middle of it all
When they all got reunited in the last chapters it was surreal lol
Kamiko tho he's got a bit of a cocky character, he wanted to prove he was the best for Matsuda, to the point of asking the past crush to do Matsuda was like okay bro you got it
I can see it as him trying to mark matsuda in a way tho, by being overly open about it, especially when they were talking (past crush and Kamiko) it was his way of saying "I have *that* kind of relationship with Matsuda"
Side notes
There's this sense of loneliness etched between the two of them
With uncertainty of whether he's only staying just because he is "lonely" so that he could "fix" him
Its because of that that Matsuda thinks he might leave just like how he did to all of those girls once they became happy
And so as to not get hurt, he pushes him away by telling him to leave soon
But they both know he wont leave
He wasn't just a guest anymore
It was nice to see him help out in detective work, and the fact that he's actually got sharp and quick thinking skills sometimes noticing things first than mc.
Other side note absolutely FUCK THAT GUY
The the ex friends with benefits
THE AUDACITY BRO, not only are you broke you had the gall to do that shit, if u have debts pay it with your OWN body dont go dragging Matsuda down u weirdo