Yotsuba's grandmother, usually called "Grandma" (ばーちゃん bā-chan) by her granddaughter, is the mother of Yousuke Koiwai and grandmother of Yotsuba Koiwai. She lives with her husband in the country, and allowed Yousuke and Yotsuba to stay at her house before they moved to their own place. She first visited her son and granddaughter's new home when she was in the area for a concert with a friend called Hiramatsu. She comments on her husband being quite incapable, as he wouldn't be able to cook, clean, take out the garbage or even bathe without her help (he was formerly hospitalized according to Yousuke). Yotsuba's grandmother is originally from the Kansai region of Japan, which still reflects in her accent to a degree according to Ena.