Maruta Tsutsumi is a supporting character in the anime Migi & Dali. He is a classmate of Hitori Sonoyama, the alias used by the twin brothers Migi and Dali when they are adopted into the Sonoyama household. Physically, Maruta is a short boy with light skin, dark grey short hair, black eyes, and prominent beaver-like front teeth. He typically wears a yellow sweater with green stripes, light brown jeans, and blue, grey, and white sneakers. He lives with his grandmother, Mrs. Tsutsumi, and is first introduced during the welcome party the Sonoyamas hold for their new adopted son.

At the start of the story, Maruta comes across as a selfish and somewhat mean-spirited child. He behaves antagonistically toward Migi and Dali, often taunting or looking down on them. However, as the narrative unfolds, Maruta reveals a more helpful and resourceful side. He undergoes a notable shift from being an adversary to becoming an unlikely but valuable ally to the twins. His motivation appears to stem from a growing awareness of the corruption and dark secrets within the Ichijou family, and he chooses to assist Migi and Dali in exposing the truth about Reiko Ichijou. Maruta possesses several advanced tools, including a camcorder, and demonstrates skill in Morse code, both of which he uses to support the twins' investigation.

In terms of key relationships, Maruta interacts most closely with Migi and Dali, starting as a bully and evolving into a collaborator. He also catches the interest of Karen Ichijou, who develops a fondness for him and regards him as impressive or cool. Maruta’s development is subtle but meaningful: he moves from a petty, disruptive presence to a clever and dependable helper, contributing his technical know-how and local insight to the twins’ mission. His notable abilities include gadgetry and communication through coded signals, which make him a surprisingly effective partner in the unraveling of the village’s mysteries.