「Asuna Hoshizuki and the Underground City of Lust」, the first RPG of a new circle Fullsky Workshop. Battle ero/pleasure corruption game set in a cyberpunk setting. The setting is「NEO Utabuki」, a cyberpunk city built underground in Japan. There, armed groups known as YAKUZA wage war daily against each other. 2045,「Matsuba Shopping District」, a small neighborhood somewhere in Japan.

「Asuna Hoshizuki」, a tsundere with massive tits who led an ordinary life there, one day got dragged into a precarious situation and was taken to NEO Utabuki by Matsuba-gumi, a YAKUZA organization, who she owned a debt of 60 million yen. To clear her debt, Asuna, with a katana in hand, has to fight hostile forces in NEO Utabuki as the captain of the special attack unit of Matsuba-gumi...