Hailing from Kyoto, he first played at Fushimi Technical High School Rugby Football Club, trained by Yoshiharu Yamaguchi, who currently serves as OB president.
Currently, he works as a high school student committee member of the Japan Rugby Football Union.
After retiring from Kobe Steel, he is still active in the instruction and the spreading of rugby, while also acting as tarento (affiliated to Shochiku Geino) in each media.
In the same year, he was appointed general manager of the Kogya High School Rugby Club and Kyoto City Social Education Committee.
In April 2008 he became a visiting professor at Kagawa University and then, Oyagi retired from General Manager of Rugby Club of Kochi Central Secondary School in December 2011.
In addition, he was appointed general manager of the National High School Physical Education League Boxing Specialist.