Voiced by: Toyosaki Aki (Drama CD) & Akasaki Chinatsu (Anime)
Chiwa is Eita's tomboy childhood friend. She is usually called "Chiwawa" (chihuahua) by her friends because of her petite physique and pair of twintails that resemble puppy's ears. She used to be in the Kendo Club starting from elementary school, but had to stop it due to a critical injury in a car accident the year before they entered high school, which prompts Eita to pursue a medical carreer in order to have her fully recovered. She does not give up easily and constantly fights Masuzu for Eita's affections. She loves to eat and especially likes meat, but is a terrible cook. She has romantic feelings for Eita but was too shy to confess until Masuzu's interference.