Youko Itoigawa (糸魚川 養子 Itoigawa Yōko) is a librarian at the Kamiyama High School. Before marriage her surname was Kooriyama (郡山).
In the 1960s she was the President of the Classics Club when she was a second-year student at Kamiyama High School. Now she works as librarian at the same school.
- Her husband is briefly shown in a semi-flashback on her age.
- Her daughter is also briefly shown during the aforementioned flashback.