Mika Harima/Dollars ArcEdit
Niekawa questions people around the city about the strongest man in Ikebukuro. After interviewing a number of information sources, including Haruya Shiki and Izaya Orihara, he gets the name Shizuo Heiwajima. Niekawa visits Shizuo and makes the mistake of mentioning Shizuo's brother Kasuka after seeing the famous actor on a sign. Furious, Shizuo throws Niekawa through the air. On his way home, he is stabbed outside of his house by Haruna and becomes one of the Saika Army. When he recovers, Haruna has him attack Anri Sonohara. He is stopped by Kyouhei Kadota and his gang, as well as Celty Sturluson and, ultimately, Shizuo Heiwajima. Although taking damage that would otherwise kill a person, he appears to still be alive and has no memory of what happened to him after being stabbed.
Kadota's Coma ArcEdit
Niekawa looks for his runaway daughter, first approaching Shinju Kuzuhara, a policewoman, and later Shiki of the Awakusu-Kai. Shiki refers him to Mizuki Akabayashi, who brings him to Mikado and the Blue Squares. When later he looks into Haruna's laptop, he discovers that Haruna is involved with the Dollars. He is revealed to be under the control of Takashi, who uses him to kidnap his daughter. He later awakens to a message from his daughter.
- He is introduced into the anime by stalking, and then conversing, with Shizuo, who stands before a theatre looking at an image advertising the movie that his younger brother stars in. When he attempts to strike a conversation with Shizuo by talking about the famous idol, Shizuo loses his temper and sends Niekawa flying.
- He is a writer and is primarily known for his articles pertaining to the strongest men in Tokyo.
- The tabloid Niekawa writes for is titled Tokyo Disaster in the second light novel and Tokyo Warrior in the anime.