I think @Liquidxlax might be on to something. Seto is framed right in the middle so he is the focus of that panel. Could be the start of a misunderstanding romcom situation where it's actually Seto the bro likes and not Anjou.
@KafukaPalazzo@NODZZ I think he is interested in Chii, but probably frustrated since she's known him so long she doesn't see him that way. But she did at least say that he's attractive and fashionable, so I think that might be where it's going. He's probably saying the rude shit to try and look tough in front of her. That explains why his sister keeps slapping him, because he probably doesn't normally act so tough except when trying to impress Chita.
@livesofflight
Usually the cliche "best male friend who's open about his perversions" don't have their own romantic story lines, so I'm interested in him. Well, not so much him, him x her.