Seiji: (stands up and points accusingly at the crowd) "DAMN YOU ALL!! I can get a girlfriend if I wanted to! So stop all this lovey-dovey crap RIGHT NOOOOOWWW!!"
After he storms out, he overhears a sports broadcast about their hometeam's losing streak of 21 games straight. It hits too close to home, causing Seiji to yell at the radio... and draw strange looks from people passing him on the street.
Seiji: (face pressed against the store window) "DAMN IT, I'M ONLY UP TO 20!!"
One more when Seiji loses his voice and has Midori speaks for him.
Seiji's out cold from mistaking his sister's tequila for fruit juice. Meaning Midori has to drag his unconscious body to answer the door repeatedly. The pizza guy runs like all hell thinking a zombie is in the house.
Seiji's reaction to seeing Midori with make up, after his sister gives her a makeover. Seiji tries to play it off, but Rin calls him on it.
Nao was only moments away from advancing to the finals, when she finally notices Midori, quickly puts two and two together, and realizes the girl she's fighting is Seiji. Her response? This.
The highlight, of the competition and the chapter, is the moment Rin bows out, after to losing to Midori. She pulls a loose thread on Seiji's shorts, and gives the audience an eyeful; especially Ayase who was at ringside! The look on her face on the last two pages is priceless!
Midori gets more than an eyeful, since Seiji used his right hand Midorito cover his crotch, causing her to spaz, then faint from the shock!
Seiji's Not What It Looks Like moment early in the manga/anime, when he tries to get Midori back into her real body by having Midori touch it. Thing is, Midori's sleeping body is almost completely unclothed. Not allowed to watch, he ends up pushing Midori's face into her own breast, just when the door opens and her mother appears with the tea. In the ensuing chaos, Seiji only just manages to escape getting lynched by a horde of angry maids.