Nangoku Prison ~Hyouryuu Shita Mujintou ga Kozukuri Shinai to Derarenai Shima Datta Ken~

Reijirou is washed up on a deserted island, accompanied by three beautiful women: teen idol Arina Nasu, her manager Natsuki, and his student Yume. Arina sees this as a golden chance to lose her virginity to her beloved 'Sensei,' but Natsuki will stop at nothing to protect her, even offering herself to Reijirou first—though her plan fails. Arita is desperate to break free from chastity, and no one can stop her. After mating with all three, Reijirou discovers two more sisters, Hatsuho and Minori Nawashiro, also trapped on the island. Five girls, one man, no rules—it's time to breed!