Shuichi Aizawa works as a detective for Japan's National Police Agency and joins the specialized unit hunting Kira. His appearance evolves from tall with a large afro to a more mature look with facial hair and shorter hair after a significant timeskip. He staunchly upholds lawful procedures, frequently clashing with L's unconventional methods. This friction peaks when the NPA withdraws funding, and Aizawa learns L withheld available financial support to test his dedication. Prioritizing his family—wife Eriko, daughter Yumi, and infant son—Aizawa temporarily resigns, causing marital strain from his absences, though reconciliation occurs later. Despite leaving the official task force, Aizawa continues investigating Kira alongside Hideki Ide. They covertly assist in Kyosuke Higuchi's arrest, coordinating police to block his escape. After L's death and Light Yagami's leadership ascension, Aizawa rejoins. He becomes the first task force member to suspect Light is Kira again, initially suppressing doubts out of loyalty to Light's late father, Soichiro Yagami. His investigation intensifies after Near reveals inconsistencies in the Death Note's rules. Aizawa and Kanzo Mogi surveil Misa Amane's residence. Noticing Light's communication with Kiyomi Takada during supervised meetings, Aizawa crafts a method: marking a hotel notepad with a subtle nail indentation. Discovering this pad replaced after Light and Takada meet provides concrete evidence of unauthorized contact, confirming Light's guilt for Aizawa. He presents this evidence to Near, though instructed not to act independently. Aizawa participates in the final confrontation at the Yellow Box Warehouse, witnessing Light's downfall. Following these events, Aizawa is appointed Chief of the NPA, succeeding Soichiro Yagami, and maintains a working relationship with Near. In the live-action film series, Aizawa's character undergoes significant reduction; his family conflicts and suspicions about Light are absent, diminishing his narrative role. Conversely, the live-action television drama expands his investigative participation and retains his early suspicion of Light. The animated film "Death Note Relight: Visions of a God" condenses the series' first arc without introducing new character-specific content for Aizawa beyond his established role. Series creators noted Aizawa was initially unintended as a long-term character. His visual design was progressively refined to appear more "presentable" as his role expanded. His eventual promotion to NPA chief resulted from a narrative choice to avoid introducing a new character for the position during the finale.