Rei Kiriyama

He is the main protagonist, whose progression is explored through the series. He is a teenage professional shogi player, currently ranked at 5th-dan (6th dan in the later part of the manga). 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.

Appearance
Kiriyama has black framed glasses and dark green eyes, clashing well with his wavy black hair, that almost looks shiny. He can usually be found in his adoptive father's old green sweater and/or his school uniform. His uniform is a simplistic design, with a white button up shirt and black pants. During colder months, he will also wear a long black coat that close with toggles.

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. Rei's complicated childhood has left him with a strained relationship with his adoptive family, socially reclusive, and thrust into adulthood and out on his own when he's not truly ready for it. As he comes to interact with the world around him (especially with regards to the Kawamoto family), he comes to understand a lot of his negative thought processes and gradually changes his outlook on aspects of his life.

Rei is generally intelligent, a genius when it comes to shogi, and more often than not, moments where he comes off awkwardly are simply due to his introverted nature. However, sometimes he will display a shocking lack of common sense - for example, at one point, Rei goes on the internet to figure out how to register getting engaged with the government. When he discovers the government doesn't keep track of such things, he rails about the state of society. Not to mention the fact that he was looking this up was because he announced his intent to marry Hina, a first-year high school student, without having mentioned his interest in her at all prior to this. He also later fails to understand why people are shocked by his proposal.

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.

Chronology
Outside his days with the 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.