A Registration of players under control (支配下選手登録, Shihaika Sensyu Touroku) is the process of notifying Nippon Professional Baseball (NPB) that a professional baseball team affiliated with the NPB has the exclusive right to sign a contract with a specific player.
(NPB Agreement, Article 52)[1] A player whose unified contract documents have been approved and published by NPB is called a Registered player under control (支配下登録選手, Shihaika Touroku Sensyu) or a Controlled player (支配下選手, Shihaika Sensyu), and under Article 68 of the NPB Agreement, a team has exclusive ownership of a player unless the player becomes a free agent.
[1][2] In general, controlled players refer to players on a team, excluding people considered Developmental players.
(NPB Agreement, Article 81, 170)[1] Players must fulfill their obligation to participate in official games (Central League Pacific League, Eastern League, and Western League) held by NPB as well as unofficial games and training conducted by teams, All-Star Series, playoffs, and the Japan Series during the contract period.
(Article 4 of the Unified contract documents)[3]