Riki Nendou is a student at PK Academy, first encountered as a freshman bully who copied Kusuo Saiki's notes and targeted him. His imposing height of 191.3 cm (approximately 6'3") and distinctive appearance—marked by a scar on his left eye, a yellow mohawk with black sides, and a mustache grown to mimic his favorite comic book villain, Baron Cola—contribute to his intimidating look. He typically wears his school uniform open over an orange t-shirt. Many classmates avoid him, mistaking his sinister appearance for delinquency. Nendou possesses an extreme lack of intelligence, struggling to grasp explanations even after repetition, and exhibits poor manners. Yet, he displays unexpected kindness: he rescues a girl who rejected him from drowning and accepts her apology, saves classmates like Shun Kaidou and Hairo Kineshi, dotes on his pet hamster Koriki No. 2, and shares food with Saiki. He deeply cares for his family, visiting the grave of his deceased father, Takeuchi Riki, whom he never met, and taking jobs to buy gifts for his mother, Midori, though his incompetence prevents long-term employment. A notable flaw is his occasional perverted behavior toward women, including Teruhashi Kokomi, often expressing preferences for curvy figures. His character arc begins when he shifts from bullying Saiki to becoming his self-proclaimed protector after Saiki covertly helps him when falsely accused by Takahashi. Nendou then declares Saiki his "partner," persistently inviting him for ramen after school and intimidating anyone he perceives as a threat. By sophomore year, Nendou, Saiki, and Kaidou form a trio viewed by peers with Saiki as the leader. Nendou's abilities include exceptional athletic strength for lifting heavy objects or overpowering opponents. His "ignorant limitation transcendence" allows him to perform impossible actions—like twisting his neck like an owl—simply because he doesn't realize they are impossible. This trait also renders his mind unreadable to Saiki's telepathy, as Nendou's thoughts process at the same slow speed as his speech. Key relationships feature his devotion to his mother Midori and deceased father Takeuchi Riki, his bond with his hamster, and his view of Saiki as his best friend, prioritizing him over others—even warning Saiki about Kaidou's perceived untrustworthiness. His interactions often involve comedic misunderstandings, like his accidental first kiss with Takahashi during a faked illness. Trivia notes include his name's kanji (力) meaning "power," with its alternative reading ("Nendou Ryoku") being the Japanese term for telekinesis. His childhood dream was to become a carpenter, and his blood type is listed as either O or B. Despite his generally low intelligence, he occasionally shows perceptiveness, such as seeing through Kaidou's fictional "Jet-Black Wings" stories.