Mitsuru Maruyama is a supporting character in Chie the Brat. He works as a police officer at the Nishi-Hagi Police Station and serves as the longtime best friend of Tetsu Takemoto, Chie’s father. Despite regarding their bond as something of a stubborn entanglement, Mitsuru continues to affectionately call Tetsu by the nickname Tecchan and remains a constant presence in his life, often trying to keep him out of trouble or covering for his misdeeds.

In his youth, Mitsuru was known as a notorious delinquent, second only to Tetsu, and was involved in various petty crimes. However, around the time Tetsu met his future wife Yoshie, Mitsuru began to reform and eventually became a respectable police officer. In his younger days, Mitsuru also harbored romantic feelings for Yoshie, though his affection was not reciprocated. He later married a former policewoman, who is skilled in kendo and once bested him in a match by landing a throat thrust that temporarily silenced him. The couple has a son named Masao, who does not appear in the main story. Mitsuru’s mother raised him as a single parent and remains a close family friend of Tetsu’s mother, Kiku.

Mitsuru’s personality is reliable and good-natured, though he occasionally shows frustration with Tetsu’s irresponsible antics. His role in the story is largely that of a steady, grounding presence among the chaotic cast. He acts as a voice of reason and a bridge between Tetsu and the law, often intervening in disputes or helping to resolve conflicts. While not a central figure in the plot, his long history with the Takemoto family and his gradual transition from troublemaker to upstanding citizen underline themes of growth and loyalty.