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 career 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. However, in the light novels she starts improving her cooking skill for Eita. She has romantic feelings for Eita but was too shy to confess until Masuzu's interference. She is the closest female character to Eita. She dislikes seeing girls getting close to Eita but becomes fast friends with the other girls.