Fourth and youngest daughter of the Tsukishima family. She is in kindergarten during Part One, and in 5th grade at the start of Part Two. Although she lost her mother at a very young age, she has a happy, energetic, and outgoing personality. Despite their difference in ages, Momiji and Kō have a friendly, sibling-like relationship. She catches for him when he practices pitching. Once, while playing catch, Aoba apologizes for throwing the ball so hard and Momiji says she is used to it as Kō's pitches are harder—to Aoba's surprise. Momiji grows up to resemble her older sister Wakaba, which surprises Akaishi the first time he meets her. Her name means "maple leaf".