Jack Seward

“Although there is no precise word for it in Japanese, a sort of "vicarious seppuku" was practiced during the Sengoku Jidai (The Era of Warfare) with the aim of saving the lives of many by the sacrifice of one life, often that of the most responsible person. For example, when Hideyoshi was warring with Mori Motonari, he decided to try to effect a reconciliation with the latter. At that time, Hideyoshi had under siege one of Mori's castles, which was commanded by Shimizu Muneharu. Hideyoshi offered to spare the rest of the garrison if Lord Mori would have Shimizu commit seppuku, to which Mori agreed.

Connected to this episode is a moving example of junshi: On the eve of Shimizu's seppuku, his favorite vassal Shirai sent a request that Shimizu visit his room. When Shimizu arrived, Shirai apologized for having his master visit his humble quarters and explained that he had wanted to reassure his master that seppuku was not difficult and that he, Shimizu, should not be concerned about what he would have to do on the morrow. So saying, Shirai bared his abdomen to show that he himself had completed the act of seppuku only a moment before Shimizu's arrival. Shimizu gave Shirai his deepest thanks for his loyal devotion and assisted him in kaishaku, i.e., he beheaded him with his sword.”
― Jack Seward, Hara-Kiri: Japanese Ritual Suicide