New boy Natsume Hiro comes to a boarding school unlike any other school in existence to solve/resolve something that happened in his past- but even that fact takes a while to emerge.
The school is a hotbed of bullying and rape kept slightly in check by a feudal organization called the Salon. The Salon protects its members from random abuse by specifying who can/must rape whom (yeah, there are must rapes here) under what circumstances, and punishing those who rape/abuse without proper permission. All this to be decided at the whim of the Salon head.
Sex at the school is both an overwhelming obsession, as befits an all-male society where there are no other outlets for stress, and a matter of down-and-dirty power politics, not unlike an American jail.
When you throw in the Byzantine institution of the Salon, you have a scenario reminiscent of the surrealistic, closed, hothouse world of British boys' schools. But the Rika world is even more bizarre than that.