I love that he doesn't just say "You're not ugly, you're cute!" or something- he says he'll like her no matter what anyone else says. It's not arguing with her self image of herself; it's getting to the actual problem he can solve. And also: It's just very, very sweet.
It's amazing how this chapter has such a great balance of funny, sad, and sweet. This secret is gonna last all of two seconds though lol, good luck to them both for taking this stress on
"Ueno doesn't seem like a good liar but..." Yeah, no shit. This secret won't last 3 chapters. Your entire friend group already knows the score, and the rest of the class have their eyes and ears open for any hint of who Ueno's mystery crush is.