Medaka Breeder is a simulation game by Taiho Games, available on Android for free. In this game, players can experience realistic killifish keeping on their mobile devices. The main features include feeding and cleaning the tank of the killifish once every three days to ensure their growth and breeding. Players can keep a maximum of 50 killifish, with up to 10 in each tank and set up to 5 aquariums. The offspring of the breeding inherit characteristics from their parents.

The game offers a mode switching feature, allowing users to toggle between default, observation, and shooting modes. Players can name each killifish for personalization and keep them in various aquarium layouts. The in-game shop offers a wide range of killifish, aquariums, and ornaments for purchase. Completing missions rewards players with items, and a premium pack is available for additional features like removing ads and enhancing gameplay.