In 1045 when the Emperor Gosuzaku passed away and the Emperor Goreizei ascended the throne and his younger parental half-brother Imperial Prince Takahito (later the Emperor Gosanjo) became Kotaitei (the younger brother of an Emperor who is heir apparent), Sukefusa as well as FUJIWARA no Yoshinobu (Togu no daibu (Master of the Crown Prince's Quarters)) were appointed to Togu Gon no daibu (Provisional Master of the Crown Prince's Quarters) and ordered to assist Kotaitei.
寛徳2年（1045年）、後朱雀天皇が崩御して、後冷泉天皇が即位し、異母弟の尊仁親王（後の後三条天皇）が皇太弟となると、藤原能信（春宮大夫）とともに春宮権大夫に任じられて、皇太弟の補佐を命じられた。