Due to memory loss, much of Eiichi Misumi’s past and true personality remains unknown, but he is shown to have a quiet and thoughtful disposition. He has expressed a strong preference for puzzle games, stating that playing them occasionally triggers fragmented memories of his forgotten past. As a result, he is rarely seen playing any other game genres, although he performs well when he does.

Eiichi is kindhearted and sociable, as seen during his first meeting with Keita Amano, where he openly expressed a desire to be friends, citing his lack of close associates. Even after Keita declined to join the Game Club, Eiichi remained friendly and continued to spend time with him, even seeking Keita’s recommendation when choosing a new game. His supportive nature extends to others as well he once offered Karen Tendō advice on how to turn down romantic confessions more gently, noting that her rejections came across as too cold.

This compassionate side was further demonstrated when he intervened to help a girl in distress, who would later become his adoptive sister. While he briefly showed passive-aggressive frustration upon witnessing Keita and Chiaki together seemingly undermining his efforts to support Karen Eiichi quickly returned to his typically calm and friendly self.

Eiichi is notably perceptive when it comes to the emotions of those around him. From early on, he recognizes Karen’s romantic feelings toward Keita and subtly encourages her to be more open about them. However, despite his awareness of others’ relationships, Eiichi himself is somewhat oblivious when it comes to his own romantic situation. He fails to realize that his adoptive sister, Riki, has developed feelings for him as a result of his kindness and heroism.

Eiichi Misumi is a young man of average height with black hair and gray eyes. He has a well-toned physique, which may be connected to his mysterious past involving an undisclosed experiment. His athletic build stands out among his peers, hinting at a background that remains largely unknown due to his memory loss.

Eiichi Misumi claims to have lost all memories of his past due to unknown circumstances. According to his account, he awoke naked in an arcade and wandered through the city cloaked and disoriented. During this time, he encountered a young girl named Riki Misumi, who was about to be kidnapped by two men. Eiichi intervened and successfully fended off the attackers, rescuing her.

Grateful for his actions, Riki who came from a wealthy family brought Eiichi home, where her parents decided to adopt him. He was given the name Eiichi Misumi, taking on the family surname. While Eiichi adjusted to his new life, fragments of his past occasionally surfaced. He discovered that puzzle games seemed to trigger faint memories and feelings of familiarity. Additionally, he experienced brief recollections that hinted at his involvement in a mysterious experiment, possibly conducted by the same men who attempted to abduct Riki.

Despite his amnesia, Eiichi led a relatively normal life under his new identity. He remained unaware of his adoptive sister Riki’s growing jealousy whenever he mentioned other girls from school, as he was largely oblivious to her affections.

Eiichi eventually enrolled at Otobuki High School but struggled to make friends during his first year. In his second year, while playing games at an arcade, he encountered Karen Tendō, a fellow student from Class 2-A. Impressed by his skills and interest in gaming, Karen invited him to join the school’s Game Club. Through her, he became friends with other members of the club and also met Keita Amano, who declined the invitation to join but still became part of their social circle.

Throughout the series, Eiichi demonstrates awareness of the emotional dynamics among his peers. He is one of the first to notice Karen’s jealousy regarding Keita’s interactions with Chiaki Hoshinomori and gently encourages her to confront her feelings. He also offers Karen advice on how to more compassionately reject confessions from boys, though she has difficulty implementing his suggestions effectively.

Eiichi builds a casual friendship with Keita, occasionally seeking his input on game recommendations. In one instance, while the two are browsing for games, they spot a suspicious individual in a brown jacket. Trusting Keita’s taste, Eiichi chooses a game based on his suggestion, reinforcing the trust and growing camaraderie between them.

The given name Eiichi (瑛一) is composed of the kanji ei (瑛), meaning “sparkle of jewelry” or “crystal,” and ichi (一), meaning “one.” His surname, Misumi (三角), combines mi (三), meaning “three,” and sumi (角), meaning “horn” or “corner.”