Rei Kiriyama

Rei Kiriyama (桐山 零 Kiriyama Rei) is the narrator and the main protagonist of the story. 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 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.

Background
Rei has had a very traumatic childhood. He mentions he was bullied at school and in the neighborhood, and couldn't relate to the other children. After his parents and sister died in a traffic accident, he was taken care of by his father's friend Kōda and became his apprentice in shōgi. Through his step-father's tutelage, he became a professional shōgi player while still in middle school. Afterwards, he decided leave home, due to feeling guilty about his presence negatively affecting his foster family. After moving out, he starts living alone in an apartment at the city of Rokugatsu-chō. However, experiencing a desire to attend school, Rei later joined a high school after a one-year delay. Rei has never had much in the way of friends, and indeed, even as a young child, his status as a shogi prodigy led him to interact solely with adults and not other people his own age. Of course, Rei's incapability of making friends is informed by the fact that Rei is the point-of-view character and his own outlook on his life.

Personality
As a result of his traumatic childhood, Rei is socially reclusive and has many emotional scars that still plague him to this day. In everyday conversion, he is meek and shy, even speaking in keigo to those younger than him. While he's never defined as having any kind of psychological or psychiatric disorders, he's frequently portrayed as a few steps outside the norm. He shows frequent evidence of clinical depression, and a very strong correlation to Asperger syndrome or high-functioning autism, with his poor social skills, limited expression (children often called him a "robot"), inability to understand others' feelings, obsession with a singular subject, etc. His biological father is even shown to have had a habit of rocking when he concentrated, a very typical behavior of autism.

Chronology
Outside his days with the Kawamoto family, however, Rei has many issues and emotional scars that plague him every day. His social skills leave much to be desired, and he typically spends time in school alone due to his inability to interact with his peers. His biological family's deaths from his early childhood still haunt him, and his strained relationship with his foster family is one of the main reasons of his early independence. Shogi itself is also a primary source of his problems, from problems of the present, such as the stagnation in his climbing of the ranks, to deep-seated issues relating to his past such as the bitterness it has caused between him and his foster siblings. Much of the story involves him coping with these issues and slowly moving past them.