Tomoe Tsukubae serves as the fifth member to join the baseball team, occupying the position of third base. She is the elder twin sister of Shizuka Tsukubae, and the two share a room in the school dormitory. While her sister favors traditional Japanese attire, Tomoe wears a sailor uniform to school.

Previously a member of the newspaper club, Tomoe is highly athletic and holds the personal dream of hitting a home run. Her primary reason for joining the baseball team was a strong crush on fellow teammate Koume, driven by a desire to be near her. Tomoe is a student in class 2-1 at her academy. Another character, Kyouko Sakurami, holds a significant crush on Tomoe, which prompted Kyouko to join the team immediately upon being asked.