Yuusuke Takazaki
Ordinary, nice, and maybe a little paranoid, Yuusuke is the typical male protagonist one would find in most anime. He is friends with the Baka Trio, yet does not share their "perverted" interests. Nevertheless, he usually finds himself forced into situations or dragged along by the Baka Trio; which often ends in misunderstandings of his true intentions with those of the Trio.
Midori Chitose
The main female lead, Midori is an outgoing and cheerful girl who seems to know Yuusuke and is in love with him. She seems willing to do anything for him, even filling out a form of perverted questions the Baka Trio gave her, hoping it will please Yuusuke
Chigusa Iino
Chigusa is the nurse at the all-girls boarding school. She came along on the trip as the girls' supervisor. The Baka Trio, especially Bacchi-Gu, are enamored by Chigusa's beauty and her E-cup breasts. Although she should be keeping the girls in order, Chigusa is very easy-going and actually encourages the girls to flirt with the boys.
Futaba Kutsuki
Futaba plays the role of the tough girl. She is disgusted by the Baka Trio and considers most of the boys in Kanenone to be perverts. Futaba even goes so far as to knock out and hang the Baka Trio (and Yuusuke) upside down by rope when they are caught peeping on the girls while they bathe.
Wakaba Kutsuki
Wakaba is Futaba's younger sister. She looks up to and respects Futaba, but has trouble refusing a favor if someone asks for it. The most defining trait of Wakaba is her potted cactus, whom she named Togemura. Wakaba carries Togemura everywhere with her and seems to be able to speak to it and sense when Togemura is talking to her.
Sanae Minami
A weak and shy girl, Sanae looks much younger than the rest of the main female characters. This has drawn the attention of Tenjin, who is attracted to "little sister" types. In fact, Tenjin wants Sanae to call him "Onii-chama", a term meaning "big brother" which merges chan and sama.
Reika Morimura
Reika is Midori's best friend and seems to know about the connection between Midori and Yuusuke. She seems to be intent on keeping the two apart, trying to put Yuusuke and Futaba together instead. Reika's motives are explained near the end of the series.