• Dull-Witted and Clueless: He lacks common sense, misses social cues, and is frequently oblivious to sarcasm, subtlety, or the supernatural. • Blank Mind: He is the only person whose thoughts the psychic Kusuo Saiki cannot read. Kusuo notes that Nendou's mind is unreadable simply because he is usually not thinking of anything at all (or his thinking speed matches his speaking speed). • Heart of Gold: Despite his intimidating, delinquent-like appearance (tall build, sharp chin, mohawk, and facial scar), he is genuinely well-intentioned, polite to strangers, and loves helping people—especially those who are weak or in need. • Deep Loyalty and Friendship: He considers Kusuo Saiki his best friend (calling him “partner” or “buddy”) and persistently sticks by him, frequently inviting him out for ramen. He is also very filial and devoted to his mother. • High Athleticism: While academically weak, his physical strength, reflexes, and athletic abilities in physical education are top-notch.
• Vocalizing Thoughts: Nendou's speed of thinking is identical to the speed at which he speaks, meaning he says out loud virtually everything that goes through his head—leaving no private thoughts for Saiki to read via telepathy. • Delivery and Tone: He has a deep, monotonous, and somewhat menacing-sounding voice (voiced by Daisuke Ono in Japanese and David Wald in English) that sharply contrasts with his actual simple-minded and good-natured personality. • Catchphrases: He frequently defaults to blunt, straightforward declarations, most notably his signature line: "Bro, let's go eat ramen!"
When Riki is a freshmen, he starts out as a bully who constantly picks on Kusuo and copies his notes. He later changes and becomes Kusuo's stalker after thinking that Saiki was the one who saved him when he was framed by Takahashi. Later that day, Riki becomes a protector of Kusuo, scaring any people passing by Kusuo and constantly pestering Kusuo to eat ramen when school ends. In a time skip, Riki is a sophomore along with Kusuo and Shun, and the three are grouped together with Kusuo seen in the center. The students think that Kusuo is the leader of their group.
