Shinjiro Chikami, nicknamed "Kamishin" by his friend Suzu Naito, attends the same rural Japanese high school. He possesses a passionate and driven personality, intensely focused on athletics. Demonstrating initiative, he founded the school's canoe club himself. His primary ambition is achieving inter-school success in canoeing and qualifying for the national championship. Generally good-natured, Kamishin sometimes exhibits airheaded tendencies and engages in lighthearted teasing, like joking that girls have crushes on him.

Within his friend group, including Suzu Naito, Shinobu Hisatake, and Ruka Watanabe, Kamishin maintains friendly relationships. His interactions with Ruka gain significance when she develops romantic feelings. After Ruka confides in Suzu, Kamishin learns of her affection, initially through his own joking accusation. They later bond over a shared appreciation for Belle's music. Ruka promises to watch him compete in the canoe nationals, a commitment he deeply values, believing her support will help him win.

Kamishin plays a key role in resolving the conflict involving Kei and Tomo. After Suzu reveals herself as Belle in "U" to gain Kei's trust, the brothers try to send their location before their abusive father cuts the connection. Using clues from the interrupted video feed, Kamishin collaborates with Ruka to deduce their location as Kawasaki, Kanagawa Prefecture, near Tokyo. This deduction enables Suzu to travel there directly to protect the brothers when authorities cannot act immediately.

In the virtual world "U," Kamishin's avatar, an "A.S.," resembles a dog-like creature with long brown fur, white cartoonish eyes, long flappy ears, a furry snout, and a black nose. A prominent scar stretches across its right eye. The avatar constantly carries a canoe paddle and wears a canoe strapped to its back, mirroring his real-world passion. The scar and persistent canoe equipment visually symbolize his dedication within the virtual space.