That guy realised that he's the only one who actually defends the boyfriend. He realised that Satoi actually has done nothing for him, other than trying to rape him when he was having a panic attack. He realised that while Satoi liked to act like he was stronger, he was not. He was pathetic and weak and has never fought for his boyfriend once. Not when his boyfriend was bullied, not when his boyfriend called himself too weird to hang out with him.
Soutarou realised that Satoi was too self-absorbed with his own problems with Mifune to care about his.
*flips table* WHAT THE HELL HAPPENED TO THAT GUY IN CH 2 *punches wall* THE ONE WHO THREW A FREAKING TRASH CAN AT THE GUYS , WHO WERE ABOUT TO BEAT UP SATOI *kicks table* WHERE TF DID HE GO??? *Trips over table leg* BRING HIM BACK *breaks ankle* AND FIGHT FOR YOUR MAN DAMN IT!!! DO NOT LET BLACK HAIR AND BLONDIE STEAL YO GIRL AND GUY (╯°Д °)╯╧╧ ヽ(`Д´)ﾉ