Ouji is the boy that P-ko kisses first when she gets to Earth. Ouji then is obsessed with the girls, knowing that something is up with them. His brother, Ouga, seems to think he's over reacting, but Ouji is determined to find out what is up with the girls.
Ouji is the first person P-ko kisses, which is sort of unfortunate since he hates bugs... having a cockroach land on your lips is enough to freak anyone out, let alone a boy who can't stand them! When he finds P-ko sitting on him, he is at first convinced the girls are terrorists.
P-ko really loves Ouji, but even if Ouji reciprocates the feelings, he doesn't show it. I believe, personally, that Ouji finds P-ko charming at least, though... even if he did think she was really, really wierd. At the christmas party of P-ko and Q-ko, Ouji sat under the mistletoe with P-ko... but he didn't give her a kiss until later, when they were being attacked. And even then, the kiss was an accident, and as soon as it happened, P-ko turned into a cockroach and thoroughly freaked out Ouji. (He hates bugs, remember?)
Ouji has pleanty of evidence to back up that the girls are not from this part of the galaxy. ^_- First he saw a flash of light, (which he assumed was from an explosion), and dubbed the girls terrorists. The next day, however, he saw them floating around a ball of light above the vacant lot outside his house. He even saw their panties, and wondered about the ones with the strawberry print. ^_- Then the next day there was a house on the vacant lot! His family dismissed it as the work of someone at night, shrugging it off as "that's progress". He found a heart shaped bracelet at the first scene (when he still thought they were terrorists), and later saw the girls flying around in their pq uniforms. P-ko noticed he had her bracelet, then flew down, thanked him for finding her ID pendant, and went back. All of this was a bit much for Ouji to take in.
Finally, Ouji confronts the girls and tells them he knows their secret... they are aliens! Q-ko begs Ouji to keep it secret, and he says he will, as long as they promise the safety of himself and Earth. The girls are happy to accomidate and P-ko tells him that they didn't come to Earth to hurt anyone, but to befriend them. Ouji is happy with this... but still thinks they're wierd.