Yoshino Mizutani

She is considered as a workaholic and is never home. It's possible that because her husband struggles with work, she works overtime to support her family. At one point in the past, she called her husband a failure because she was fed up with his failed attempts at work. She appears only when talking on the phone with Shizuku or sending her a fax. When it's Shizuku's birthday she can't leave work to see her. Shizuku gets a little depressed, but Haru Yoshida then lends her his cellphone to call her. Yoshino says sorry, because of work she can't go to see her, and she'll talk to her later. Later Yoshino calls Shizuku and they talk about school, friends and Haru. She tells Shizuku she doesn't have to pick between studying and Haru, because she can get both if she works twice as hard. (Source: tonari-no-kaibutsukun.wikia.com)