On April 3, 2005, Nashiro fought Japanese Super flyweight champion Seiji Tanaka. The two had often sparred and trained together, and Nashiro won by TKO in the 10th round, winning the title. However, Tanaka dropped into a coma after the fight, and died two weeks later from a
subdural hematoma. Nashiro went into a sort of shock state after Tanaka's death, and seriously contemplated retirement from the guilt he felt. He kept himself away from boxing for over a month, until he met Tanaka's father at
Masamori Tokuyama's WBC title defense. Tanaka's father told Nashiro to not worry about what happened to his son, and to continue his boxing career. Nashiro paid a visit to Tanaka's grave in
Tottori, Japan, to pay his respects, after defending the title won from Tanaka. Nashiro's struggle was documented on an episode of the Japanese TV show
Kiseki Taiken! Unbelievabou! aired on February 22, 2007. ==World title==