Human beasts Yagi and Okami live on a planet called Serian, which is just like Earth. They were sent out on infiltration training to Earth together when they entered high school. They were once close with each other, but now there's nothing but fights between them whenever they open their mouths. The story starts three days after they've arrived on Earth prescribed with human shifting medicines and estrus prevention pills. Incidentally, Yagi entered his estrus period, but his reactions were weird... Worried, Okami tried to talk it out with him, but got pulled in and got his nape bitten?! (Source: Media Soft, translated) Included one-shot: Usagi to Neko no Hatsujou Jijou