When Yoshimoto was killed in the Battle of Okehazama and the IMAGAWA Clan became disorganized, "Jiro Saburo Motonobu SERATA" and his comrades captured Hamamatsu-jo Castle and tried to occupy Mikawa Province, but were defeated by Ieyasu (Motoyasu at that time), and forced to submit to him and return his son, Nobuyasu, and became the vassal of Ieyasu.
そして桶狭間で義元が信長に討たれて今川氏が混乱すると、「世良田二郎三郎元信」は同志を集めて浜松城を落とし、さらに勢いに乗じて三河を攻略しようとしたが、松平元康と名乗っていた家康に敗れて降伏し、信康の身柄を元康に返還することを条件に罪を許され、その家臣になったという。