He fought at the Battle of Suriagehara in 1589, participated in suppression of the Kunohe Rebellion in 1591, and then served with the Korean campaign in 1592.

After the Bunroku Campaign, Hideyoshi suspected Masamune of treason, it was Tsunamoto who pleaded on his lord's behalf.

Another story has Tsunamoto change his name to "Moniwa Nobumoto" (茂庭延元) to placate the Taikō; according to sources, Hideyoshi was superstitious of the "Oniniwa" name because of its meaning, "the garden of the demon".

After spending several years as an attendant for Masamune's son Hidemune, Tsunamoto retired from the Date clan and became a Buddhist monk.

In NHK's 1987 Taiga drama Dokuganryū Masamune, Tsunamoto was played by Takehiro Murata.