Shun Matsubayashi is a second-year student at Fujioka East High school and a founding member of its new karuta club.
He is Shun's younger brother.
Arata is Shun's upperclassman, whom he is helping to form a karuta club with. He calls Arata "Arata-niichan".
Shun and his brother have known Arata since childhood, having also been members of the Nagumo Karuta Society. When they were both accepted into Fujioka East High School, they started on establishing a karuta club there.