Shuichi Aizawa serves as a dedicated member of the Japanese Task Force investigating Kira, consistently maintaining a professional demeanor and prioritizing lawful procedures. He frequently expresses frustration with unconventional investigation methods. His physical appearance evolves significantly, initially featuring a large afro before transitioning to shorter hair with facial hair in later years. Family responsibilities profoundly shape his decisions throughout the investigation. He has a wife named Eriko, a daughter named Yumi, and an unnamed infant son. Marital strain develops due to his extended work absences, highlighted during an emotional park encounter where he tearfully reunites with his family. The manga does not clarify whether these family issues resolve, though the anime briefly depicts Yumi in later episodes. Aizawa exhibits persistent skepticism toward authority figures, specifically questioning L's methods regarding surveillance tactics and financial transparency. This distrust peaks when L withholds information about Watari's financial support during the NPA funding crisis, prompting Aizawa's temporary resignation from the Task Force to prioritize his family's financial security. Despite resigning, he continues assisting the investigation covertly with colleague Hideki Ide, notably coordinating police forces during Kyosuke Higuchi's arrest. Following L's death and Light Yagami's ascension as the new L, Aizawa returns to the Task Force. He becomes the first member to suspect Light of being Kira, initially suppressing these doubts out of respect for Light's deceased father, Soichiro Yagami. His suspicions solidify after Near reveals the falsity of the Death Note's 13-day rule. To confirm his theory about Light communicating with Kira proxy Kiyomi Takada, Aizawa employs a practical technique by marking hotel notepads; the disappearance of these marks provides tangible evidence of secret communications. Aizawa shares crucial information with Near, confirming key details about Light's confinement period that aid Near's investigation. During the Yellow Box Warehouse confrontation, he witnesses Light's exposure as Kira and subsequent demise while carrying the Task Force's Death Note per Light's instructions. In the series conclusion, he assumes the position of deputy director of the NPA, succeeding Soichiro Yagami. This promotion occurs because the creators sought an established character with police connections and prior interaction with Near, dismissing other Task Force members as unsuitable due to insufficient development or perceived incompetence. Personality assessments describe him as grounded, rule-abiding, and professionally dedicated. He frequently chastises colleague Touta Matsuda for impulsive behavior and expresses annoyance toward Misa Amane's mannerisms. His lawful approach contrasts with others' methods, exemplified when he prevents Matsuda from killing Light during the confrontation. Across adaptations, his portrayal varies: the film series minimizes his suspicion of Light and omits his family conflicts; the TV drama amplifies his investigative role and early skepticism toward Light; the musical production keeps him with the Task Force after the FBI killings, though his solo parts were reassigned in later Japanese productions.