Sister Ishida

Ishida's older sister. She is significantly older than him as she already graduated from college when he was still in elementary school.

[Spoiler] Curiously, she is the only character with lines whose face is never seen; even her husband and daughter are shown and get more screen time than her. According to Ishida, his sister had dated numerous men, one of whom has a younger brother who was bullied by Ishida; this event probably led to his breakup with her. Later, she dated a Brazilian man named Pedro, this time, her relationship stuck and she had a daughter, Maria, with him. The final chapter reveals that she is expecting her second child with Pedro. [/Spoiler]

(Source: Wikipedia)