[DTogo]

What's the Japanese term for falling on your sword to save a superior from destruction at his own hand?

The terms for ritual suicide by slitting one's abdomen are seppuku or hara kiri , whereas simple suicide is jisatsu or muri shinju when a parent (usually a mother) kills herself with a child/children. Let me consider the exact context of the situation in your question.

[cogitator]

Let me consider the exact context of the situation in your question.

There may not be a known phrase for that act -- but it seems like there should be.