Omitsu serves as the popular belle of Ragtag Town in Edo, working as a waitress and cover girl at the tea shop "Mitsuya," sometimes localized as a coffee shop or restaurant. She is acknowledged as Goemon's girlfriend, though their relationship features his occasional fear of her volatile temper and her tendency toward jealousy if he interacts with other girls. Omitsu frequently becomes a target for enemies, not always tied to Goemon's conflicts, making her a recurring damsel-in-distress.

Her debut occurs in "Ganbare Goemon! Karakuri Dōchū," where she appears as a non-hostile character wandering villages. Players gain rewards for rescuing her but face penalties for causing harm, establishing a series tradition of protecting civilian women. In "The Legend of the Mystical Ninja," she appears as a minor character living next door to Goemon and participates in a concentration minigame; matching her cards awards money.

A pivotal moment unfolds in "Mystical Ninja Starring Goemon" when Omitsu is inadvertently transported into space following Kyushu Island's ascension. Goemon fails to warn her, stunned by her rugged appearance. The heroes later discover her operating her tea shop in the transformed Sogen Town on the spaceborne island, where she thrives amid the chaos, demonstrating resilience. She provides critical guidance by directing the heroes toward the villains' location.

In the anime series, Omitsu’s role expands. She prepares a special "Power of Love" ohagi (rice ball confection) that uniquely empowers Goemon to summon and maximize the strength of the giant robot Goemon Impact. This ohagi becomes essential for his battles against the demon lord Makuamuge’s minions. The anime also reveals her as the granddaughter of the Wise Old Man.

Omitsu features in other media, including the OVA "Ganbare Goemon: Jigen Jō no Akumu," where aliens kidnap her, prompting a rescue mission by Goemon and Ebisumaru. After an alien minion transforms his leader into a handsome prince, Omitsu instantly falls in love and agrees to marry him. The spell repeatedly wears off, however, causing her to punch the alien each time he reverts, highlighting her comedic reactivity. In "Goemon’s Great Adventure," she requires rescue after being hypnotized by the villain Bismaru.

Her personality blends cheerfulness with emotional volatility. She expresses worry and loneliness over the dangers Goemon faces, yet exhibits fierce anger when provoked. This duality extends to her occasional unawareness of Goemon’s romantic interest, creating a dynamic where his efforts to protect or impress her often go unnoticed.