Chiaki Mukai is the captain of the observation ship Penguin Manju Go in the anime A Place Further Than the Universe. He is a middle-aged man with a calm and authoritative presence.

With a background in the Japanese Self-Defense Forces, Mukai previously served as the captain of an Antarctic observation team for the SDF. When the decision was made to launch a civilian research vessel, he was asked by Gin Tōdō to assume command, a role he accepted at her request. Gin holds a deep trust in his abilities, and his reputation as a capable leader is well-established among his peers.

Mukai's personality is marked by a significant shift with age. In his younger years, he was purportedly known for being a strict and tough individual. However, as he has grown older, he has mellowed considerably, developing a calm and collected demeanor. This evolution has earned him the respect of his crew, who trust him implicitly for his ability to make cool-headed and sound judgments, even in high-pressure situations.

In the story, Mukai serves as the figure of authority and stability for the expedition. He is responsible for the safe navigation of the ship and the well-being of everyone on board, including the four main girls on their journey to Antarctica. Through his previous experience, he is aware of the strained relationship between his old friend Gin Tōdō and Shirase Kobuchizawa, as this information was shared with him by Kanae Maekawa. This knowledge gives him a unique understanding of the emotional undercurrents tied to the voyage. While not a central character, his role as captain is crucial, providing the logistical and leadership backbone that makes the civilian expedition possible. His notable abilities lie in his seamanship, leadership, and the capacity for calm, decisive action born from years of experience in extreme environments.