After graduating from Hitachi First High School in Ibaraki Prefecture, Yoshino attended Waseda University.
During his time in Waseda University RFC, Yoshino, along with Kazuhiko Honjo and Makoto Tsubuku, was one of the "three crows" and became a star player.
Suntory was in the first round of the All Japan Rugby Championship against Kobe Steel, who was in the seventh consecutive match of the tournament.
Despite the 20-20 draw, he had the right to enter the semi-finals being the top try scorer of the tournament, preventing Kobe Steel's eighth consecutive win.
In the final match against Sanyo Electric, both sides tied 27-27, but since Suntory had the higher number of tries, they had the right to participate in the Japan Rugby Football Championship.