Koei Tecmo’s Omega Force partnered with Game Freak to develop Pokémon Pokopia.
Omega Force is a development team within Koei Tecmo, the Japanese video game company. The studio was selected because of its experience with sandbox and construction-oriented game design, including work connected with Dragon Quest Builders 2.
The partnership gave Pokopia a division of responsibilities that matched its concept. Game Freak brought long-standing Pokémon development knowledge, while Omega Force contributed experience with systems built around creating, modifying, and managing spaces.
Koei Tecmo is the company name, and Omega Force is the specific development team. They are related but not identical answers. Nintendo and The Pokémon Company were publishers, so neither should be substituted for the company behind the co-developing Omega Force team.