Geminism is a short, linear visual novel that tells a dark and mysterious story set in Tokyo at 2am. The story centers on identical twin sisters Kikyo and Shinku Hirosoma, who find themselves in a standoff under a moonless sky, armed with homemade weapons. Despite being twins, they have a tense relationship: Kikyo is gentle and naive, while Shinku is perpetually irritated. Two mysterious men in black — the bandaged, old-fashioned-speaking Awasumi Yamaga and the long-haired, clumsy Tsukishiro Tsukishiro are mysteriously drawn into this nighttime standoff.