A very shy and insecure young woman.
She gave birth to Sana when she was only 14. In the manga, it is revealed that her uncle made her pregnant, and she gave birth in a bathtub. Keiko says that she was deeply in love with Sana's birth father, but he has passed away. When Misako finally meets her, after Keiko provides proof of her connection to Sana, she slaps Keiko and says that even animals know they must take care of their offspring. She also arranges for Sana to meet her.
Sana was worried about meeting Keiko because she feared Misako would give her up; she discovers that Misako had the same worry—that Sana would leave with Keiko. After meeting Keiko, Sana and Misako conclude that what defines family is what's in the heart, and they are truly mother and daughter. After meeting Sana, Keiko asks if it is possible that one day Sana would come to live with her. Sana gently but firmly states that she considers Misako as her mom, although she is grateful to Keiko for bringing her into the world.
