Monster Breeder is a free role-playing game developed by Poppin Games Japan Co. Ltd. for the Android platform. The game revolves around raising and leveling up monsters to enhance their basic stats. Players can also strengthen their attacks and skills through individual training.

One unique feature of Monster Breeder is the Soul System, where players can equip souls to their monsters to grant them special abilities. This allows players to create original and one-of-a-kind monsters.

The game features a real-time command battle system, where the type of attack changes depending on the distance between players and opponents. Players must strategically position themselves to win battles.

Monster Breeder offers three battle modes: Story, where players aim to become a monster master; Descent, where powerful monsters appear in dungeons and players can obtain rare monsters by defeating them; and Arena, where players can compete against breeders nationwide to become the top breeder in Japan.

The app is available for free, with some optional in-app purchases available.