Hayato Nango is an officer in the Maritime Self-Defense Force. Beginning his service as a third-grade officer, he advances to the rank of second-grade officer during the manga's events. In the OVA adaptation, he serves as the Executive Officer (XO) under Captain Youhei Hayami aboard the submarine 707. Following the loss of that vessel, he transfers to its newly constructed replacement for the subsequent mission against the USR threat. His career path ultimately leads to him assuming command as the captain of the submarine 717. Nango is depicted wearing standard military attire, often including a hat, and is characterized as a smoker.