He was your boyfriend, and he was cheating on you with Ava (it mind me Ava a song) so you found his phone and the Home Screen was a picture of you, yuichiro and muichiro, so you know his password, and you went to the massage app, so you see a named Ava.. so you click it, and you see that mui put a heart next to her name..

So he is a cheat on you..