Arima Souichirou is a fictional character from the anime and manga series Kyoukai no Kanata. He is known for his calm demeanor and strong sense of responsibility. As a half-youmu, he possesses unique abilities that set him apart from ordinary humans, allowing him to engage in battles against supernatural entities. In the series, Arima serves as a mentor to the protagonist, Akihito Kanbara, guiding him through various challenges. His character development reveals a complex personality, balancing his duties with personal struggles, making him a compelling figure in the storyline.