Kame(Hiroto) kouki and this other guy they are the three protaganist of the show that who are good friends since young. they were going to the habour front or something after fishing to sell the fishes (?!) and suddenly the Haruka (Nao) and Toda came running in their direction and they dirtied Nao`s dress (well she is some prissy princessy kinda missy in the show, most probably not character wise but status wise only) and that night there was a party held between Nao`s school which is some for-the-elite-lady`s-girl`s university and some elite-boy`s-university... and for some reason Hiroto sneaked into the party and met her. so naturally Nao mistook him as a student of that elite university and Hiroto too (IMO rather idiotly) lied about his identity that he is from that school`s medical segment and since then everytime Kouki and the other guy meet them, they have to lie about their identity as well... since I think Nao misunderstood that they are all from that univeristy. And at the end of the desription, they added one random line that Hiroto fell into the pool with Nao.
well. 10/14 till all mystery unlock themselves xD
and the character relation chart shows that Kouki will fall in love with Toda Erika... x) and his character description writes that, he is generally very cheery (*coughswhatsnewcoughs*) but is weak when handling girls <3