Kenjiro Katagiri, commonly called Kenji or Ken, is a Caltech student recurring in official media. The younger son of Dr. Kunio Katagiri, he has an older brother, Shinjiro, a summa cum laude graduate. Hailing from a Nagoya medical family, Kenji faced intense academic pressure alongside his brother, fueling his perfectionism. His parents' divorce resulted in Kenji and Shinjiro alternating homes weekly. Revised continuity reveals his family used financial influence to secure his position as valedictorian, displacing the originally slated classmate.

Kenji stands approximately 5 feet 7 to 8 inches tall with short black hair and blue-green eyes, typically wearing thin, black-rimmed glasses. He consistently appears in semi-formal attire, favoring dress shirts, slacks, and leather shoes.

Academically driven and highly competitive, Kenji carries the label of overachiever, constantly vying for top rankings. He views classmate Léa Navarro as qualified competition, maintaining a stance of friendly rivalry. Despite this, he displays notable arrogance and a tendency to look down on peers like Cameron Mendes, Red Ordonia, and especially Hiro Hamada. His father's distant behavior influenced Kenji's reserved nature, though he consciously strives to treat women better than his father did. Kenji engages in subtle, unstated flirtation with Léa, never explicitly confirming romantic feelings. His reserved communication contrasts with moments of deliberate assertiveness regarding his intentions toward Léa, which aggravates Hiro.

Kenji's name, meaning "intelligent second son" in Japanese, reflects his familial position and academic prowess. He is roughly four to five years younger than Shinjiro. Narrative hints suggest he may identify as asexual, paralleling another character from related media. Among characters created by writer Michael Williams, Kenji ranks second in intelligence, surpassing Kenzo Grey but below Rei Sotaro. He dislikes the phonetic similarity between his name and Hiro's, both ending in "-iro".