One day, Nezumi Otoko meets Yamamoto, a JAXA employee. Yamamoto is working on a plan to terraform Mars, aiming to create an environment suitable for living organisms, and is looking to have a Kappa astronaut. Sensing a lucrative opportunity, Nezumi Otoko entices the Kappa, Kasuke with the idea that being the first yokai on Mars will make him incredibly popular with girls. They visit JAXA, but... Humans × Yokai × Space! An extraordinary collaboration begins!