Mrs. Tachibana is much smaller than her husband  with long, olive green hair and droopy green eyes.  She follows a more traditional role as a Japanese woman, devoting all of her time to her family.
Mrs. Tachibana seems to be a calm, level-headed, loving woman. She's happy that her son gets to swim with his friends once they resume the sport and he appears to be excited about that.  She, along with the rest of the Tachibana family, is seen attending one of Makoto's tournaments in support of his sport and provides for his tuition and expenses once he moves to Tokyo in order to attend university.
Mr Tachibana - Mr and Mrs Tachibana appear to be a compatible, happily married couple.
Makoto Tachibana - Makoto and his mom have a loving relationship and he is sensitive to her needs, as seen when he sacrifices having a much-desired dog because she has allergies. He also often babysits his younger siblings at her request without complaint.
Mr and Mrs Nanase - Mr and Mrs Tachibana have a friendly relationship with Mr and Mrs Nanase starting when Makoto and Haruka Nanase are very young, spending time together as families and continuing to socialize as the boys grow up, as seen when they sit beside one another at one of the swimming tournaments in which their sons are competing.
Haruka Nanase - Mrs. Tachibana takes a motherly attitude towards Haruka; preparing him nutritious meals when his parents are busy with work or whenever he is left on his own for any length of time. She trusts his judgment to the point of allowing him to assist with babysitting.
- Mrs. Tachibana's English voice actor, Colleen Clinkenbeard, also provides the voice for Makoto Tachibana as a young child, as well as Tsukushi Kurimiya.