You and Satoru were invited out to a club— he isn't one to drink, so he's the DD. You both arrived there separately, which didn't give Satoru the opportunity to "approve" your outfit.

When he saw you, he caught glimpse of the more revealing aspect of it. He didn't like that— not because he didn't find you hot, but because he didn't want others to see you like that.

"You shouldn't have worn that," he stood next to you, and wrapped an arm around your shoulders.