Ooo I'm so curious, what did the brown haired guy see, to make him glare like that

I think its because the uke usually gets sad when he leaves, but dis time he told him to go ahead. So he knows something happened

SPOILER ALERT:

Actually, he saw a hickey on the uke's neck.... which is caused by the seme during their love making, so he was shocked who he was meeting up with aside from him... And just to tell you, he's really possessive...

He intentionally put the hickey on the uke when he took the uke home it's for the brown haired guy to see it. It wasn't when their making love.