Heiji Rebellion
Tomonaga accompanied his father and two brothers, Minamoto no Yoshihira and Minamoto no Yoritomo, fleeing Kyoto following their defeat in the Heiji Rebellion in 1160. Tomonaga had been wounded on Mount Hiei. The four made their way through snowstorms to the east in an attempt to levy troops. Yoshihira and Yoritomo went on ahead, while Tomonaga lagged behind. Tomonaga asked his father to kill him so he would not fall into the hands of the enemy. Yoshitomo obliged his son. Shortly afterwards, Yoshitomo was also killed.