|Relations||Suguru Koshigaya (son)|
Komari Koshigaya (eldest daughter)
Natsumi Koshigaya (youngest daughter)
Yukiko is known to be particularly strict, especially towards Natsumi. She tends to yell at Natsumi a lot because she tends to disobey her... a lot. Yukiko is a very disciplinary mother and wants her children to obey her. It would seem that her parents may have been very disciplinary towards her seeing as she is towards her children especially when they lie. She praises the other children such as Renge and Hotaru because she wishes her children would follow their example.
Yukiko is an older woman with dark hair and grey eyes. She has pale skin and she is usually shown with and angered expression on her face. She is mainly shown in a tee-shirt and slacks.