Rei Kiriyama 桐山零

He is the main protagonist, whose progression is explored through the series. He is a teenage professional shogi player, currently ranked at 5th-dan. He is widely lauded in the shogi community as the fifth shogi player to become a professional in middle school. Using his salary combined with his life savings, he lives in his own apartment while juggling between his official matches and high school. By the time the story begins, Rei is also a frequent visitor of the Kawamoto residence, where the family treats him as one of their own despite his initial reluctance to become close with them.