"Mitsudomoe" is a comedic manga series centered around the daily lives of the Marui triplets—Mitsuba, Futaba, and Hitoha—and their interactions with their homeroom teacher, Satoshi Yabe, as well as their classmates. The triplets, though identical in appearance, have distinct personalities that often lead to chaotic and humorous situations. Mitsuba is the most mischievous and outspoken, frequently causing trouble with her bold and unpredictable behavior. Futaba, the most athletic and tomboyish, often finds herself caught up in Mitsuba’s schemes despite her more straightforward nature. Hitoha, the youngest and most reserved, is a bookworm with a vivid imagination, often interpreting events in a dramatic or fantastical way.

The story primarily takes place in their elementary school, where the triplets’ antics create a series of misunderstandings and comedic scenarios. Satoshi Yabe, their teacher, struggles to maintain order in the classroom while dealing with the triplets’ eccentricities. His efforts to discipline them often backfire, leading to further chaos. The triplets’ classmates, including the shy and easily flustered Sugisaki and the sharp-tongued Shiori, also play significant roles in the series, often becoming unwitting participants in the triplets’ schemes.

Family dynamics are another key element, as the triplets’ father, Shinichiro Marui, is a single parent raising them after the death of their mother. His attempts to balance work and parenting are frequently challenged by the triplets’ antics, adding another layer of humor and heart to the story. The series explores themes of sibling rivalry, childhood innocence, and the challenges of growing up, all while maintaining a lighthearted and comedic tone. The humor often arises from the triplets’ misunderstandings, exaggerated reactions, and the absurdity of their situations, making "Mitsudomoe" a blend of slapstick comedy and heartfelt moments.