Tomori won the Japan's inter-high school championship in the 45 kg class in 1977, and compiled an amateur record of 16–4 (3 KOs) before turning professional.
In March 1979, Tomori won the annual Japanese boxing series, All-Japan Rookie King Tournament in the junior flyweight division.
[5] On April 13, 1982, Tomori was scheduled to fight against Amado Ursúa for the WBC junior flyweight title at the Korakuen Hall.
He trained under the guidance of Eddie Townsend who signed a deal with Misako Boxing Gym in March of that year.
[10][11][12] Misako protested the decision of the judges to the WBC,[13][14] and Tomori had a rematch with Zapata as a challenger at the Kuramae Kokugikan on November 30 of the same year.