Nowake used to be an assistant to Frosti and was also Yae Oda's former classmate.
Five years ago when an accident befell on director Oda and her daughter Alisa, Nowake refused to donate blood, blood of the same type with Alisa. Yae Oda had a grudge on him ever since that incident. She considers her daughter's death as Nowake's fault.
In the manga, he refuses to donate blood, but in the anime, he's a scientist that Oda gets tricked by. Her daughter has a fatal sickness and he has a "miracle drug" that will save her, but isn't exactly legitimate. Oda trusts him and has the drug injected into her daughter. Nowake knows that the Alisa won't live, and after he's speaking on the phone, Oda discovers that as well. Oda loathed both Frosti and Nowake and hired Banten shinobi: Tobari, Miharu, Raimei, and Kouichi to assasinate them during a convention in exchange for Togakushi Village's kinjutsu scroll: Izuna Shingan.
Kouichi hypnotizes Nowake
After Kouichi killed Frosti, he hypnotized Nowake so that he admitted that he was the one who killed Frosti.