Didn't mean to dislike cause really, WTF Mao!?
He confessed in a really vulnerable time to Hisashi and to all he knows, Hisashi is very in love with his ex. He doesn't know that Hisashi was also seeing him in another light since before breaking up with his boyfriend, so while it was a great moment to Hisashi, Mao is thinking that he overstepped and probably Hisashi was also going along with the kiss because he was needed.
Exactly, Mao thinks he took advantage him in his vulnerable time and so put the breaks on things so he would not abuse their relationship with each other.
Plus, he might be thinking that the relationship could be mended, 2 years is a long time to be with someone.
aka misunderstandings that would disappear if he would listen to the other party..
But I also get not wanting to be hurt when he has an important project to focus on
MAO WTF