In fact, Norimasa IMAGAWA was appointed to Seii fukushogun by the Imperial Court, his son Noritada IMAGAWA got preferential treatment called 'one family name in the country' from the Muromachi shogunate family so that only he and his descendents were allowed to use the family name of Imagawa.
実際に今川範政は朝廷から征夷副将軍に任じられ、その子今川範忠は永享の乱の戦功によって室町将軍家から彼とその子孫以外の今川姓の使用を禁じるとする「天下一苗字」の待遇を受けた。