A gamer is magically summoned into a parallel universe, where he is chosen as one of four heroes destined to save the world from its prophesied doom.

Two children who got swapped at birth grow up to become engaged to each other. It's an arrangement neither of them like, at first.

Together with her humanoid friend Reg, a young girl named Riko hopes to one day solve the mysteries surrounding the endless chasm known as the Abyss.

Aoi is startled to see her sister’s ex-boyfriend, who’s somehow still the same bright-eyed kid he was 13 years ago, before tragedy tore them apart.