As you said 'for you'. Again I'm not tryna make an argument but just to say: you want them to have a 3p, that's why these facts are becoming
invisible to you since you're ignorant about it because your only interest is them getting together. That's why every finger is pointing to pleasure for you (peace out)
You do know that the butt can not only clench from pleasure, but from disgust too right? In yaoi you see many scenes where the uke's butt clenches from pleasure to the point that you forgot reality. This is also backed up with him saying 'that's not it (when the blonde said how dare you feel good from his kiss) '
I love Naru intruding while they're doing it. And please! that kiss to Masato