Shōta Raidō enters high school determined to make one hundred friends, motivated by a friendless middle school past where his tall stature and perpetually stoic, intimidating expression made others avoid him. He possesses short black hair, brown eyes, and that same stern expression, rarely shifting despite strong internal emotions. His school uniform—a white shirt, black pants, black belt, and white sneakers—emphasizes his notably tall frame.

Outwardly calm and stoic, Raidō's internal world is highly expressive and imaginative. He frequently conjures elaborate, absurd delusions to explain everyday events, like attributing a classmate's messy look to gang fights or interpreting quietness as secret death metal fandom. He acknowledges this tendency is problematic but defends it as scenario preparation. Despite social anxiety, he acts boldly when needed, initiating reconciliations or openly declaring affection. His broad knowledge in economics, science, law, history, and sports fuels his convoluted theories, aiding practical actions like identifying edible plants. He also cultivates acute hearing to comprehend near-inaudible speech.

His character centers on his bond with Reina Aharen, his seatmate. Their first meeting occurred in childhood during sandbox play; mistaking her for a boy named "Rei," he promised to meet again, unaware she was moving. They reunite in high school, where her extremely soft voice and fluctuating personal distance confuse him. Recognizing her communication struggles, he befriends her, making her his first high school friend. Their connection deepens through shared lunches, arcade visits, karaoke, studying, and games. During a camping trip, Raidō confesses his feelings, prompting a reciprocal kiss from Reina that temporarily complicates things due to misunderstandings. Their relationship solidifies when he publicly reaffirms his love during a confrontation with Mitsuki Ōshiro, becoming official partners. As a couple, they retain their quirks while offering mutual emotional support during insecurities like future career doubts or athletic anxieties.

His relationship with Mitsuki Ōshiro starts antagonistically; suspecting him of manipulating Reina, she stalks them. Witnessing his genuine care, she gradually accepts him, joining their friend group. Tensions flare when she misinterprets the camping kiss and challenges him to a reversi game demanding he cut ties with Reina if he loses. His victory and emotional declaration of love resolve the conflict, strengthening their friendship.

Family includes a junior high sister who initially sees him as "sort of an odd guy" but worries about his friend-making ability, hinting at underlying care. He lives with his family; parental details are unspecified. Reina's siblings form bonds with him: Ren views him as a brother figure, while Eru initially resents him for "stealing" Reina's attention but softens after seeing his consistent kindness.

Beyond high school, Raidō becomes a successful author, marrying Reina and starting a family. His writing includes "Aharen-san wa Hakarenai," based on their experiences. Later, he joins a space expedition to Mars, temporarily separating from his family but planning to return. His granddaughter discovers Reina's diary chronicling their youth, which he encourages her to read.

Distinctive traits include his verbal tic ending sentences with "じゃね？" (ja ne?, "innit?"), a competitive streak often leading to losses against Reina in games, a collection of bedside items gifted by her (including figurines and life-size models), and sharing a birthday with Reina.