Rei Kiriyama

Rei Kiriyama is the narrator and the main protagonist of the 3-gatsu no Lion anime and manga.

Rei 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.

Appearance
Rei has a messy, jet black hair and has gray eyes. He wears a white buttoned shirt, gray slacks, blue & white rubber shoes and thick black glasses.

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.

Trivia

 * Rei was isolated from his peers when he was younger, and he once mentioned that he was usually the target for bullying as a child.
 * 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.