In 1590, when Ieyasu TOKUGAWA started to rule the Kanto region, Chikamasa was granted the land Mitsukura (or Mikura) in Gunma district, Kozuke Province, capable of producing 5,500 koku of rice (1 koku weighs about 150kg), and became independent of the head house.
天正18年（1590年）、徳川家康の関東入りの時、上野国群馬郡三蔵5500石を賜り、宗家より独立。