He is the 23 year old main protagonist of Barakamon. He is a professional calligrapher and after getting criticized by the museum curator, he got mad and ended up punching the curator. He was later sent to Gotou Island to reflect on what he did and learn to create his own style of calligraphy. However, the people in the island are too care free to the point that they do not take Seishuu seriously and often cause trouble for him.