Sato Mayumi (佐藤真由美) was one of the original members of Onyanko Club as member number #10. She was fired from the group following the "Shuukan Bunshun Kitsuen Jiken" scandal that happened just before the group was set to debut
- Name: Sato Mayumi (佐藤真由美)
- Birthdate: December 25, 1967
- Birthplace: Saitama Prefecture
- Blood type: O
- Height: 158cm
Sato Mayumi was one of the original members of Onyanko Club when she was one of many girls that won the All Night Fuji-sponsored contest for a new idol group in 1985. However, she was fired on April 25th, 1985 after a tabloid published photos of several members smoking in a café despite being under-age. However, unlike the others, only her skirt was visible in the incriminating shots but she was still fired. The scandal became known as the "Shuukan Bunshun Kitsuen Jiken". At that time, Onyanko Club had not yet released their first single and were still relatively unknown, making her departure from the group unnoticed by the public's eye.
Her whereabouts following her retirement are unknown. There have been rumours of her being elected as Miss Ice Cream in 1987 or became a model.