I am leaning towards the cop, since he is a bit obsessed with Yamato, and he was introduced really early, he also have almost as much page-time as Shogo. (︶︿︶)＝凸 If you've peeked on the raw Scans for volume 4, You will see Yamato's high school Days, there might be a rekindling flame from those pages.
The Cop and the Guy you see in Vol.4, aren't the same person. Even if they look like twins (lol).
You won't see the cop anymore. At least not until Vol.6, which I didn't read yet.
The guy in vol.4 is a senpai of Yamato and Shogo.
I know they aren't the same people, or else cop-san wouldv'e recognised him from the beginning. but that kiss with shogo and Yamato was real nice and they were getting all chummy. Shogo is so not 100% straight
Wait for the next chapter.
It is almost done ;)
Hoping for more..... its good , but its hard to decide who's gonna suit fot yamato, either tamaki or
shogo ( ikindalikehim ) or the cop..shud i also wait for kippei to grown up ? haha !