The way Tsubasa and Tachibana's worried (?) expression being shown after the other when they were about to kiss shows regardless of what Tachibana thinks he feels at that moment, he and Tsubasa feels the same way at that moment, they were uneasy about the kiss. His expression wasn't even shown when Tsubasa said I like you to Yuu. Meaning his reaction to this kiss between Yuu and Tendou
whom he said he only thinks like a sister
is important.
This is why Tachibana is such a complex character. What he says and the expression he shows (and the highlight being given by the author) just doesn't match at all. So frustrating.