Used as a noun meaning 'self' or as a suffix attached to a personal pronoun or name for emphasis, like 'I myself' or 'the person themselves'. Common in both formal and everyday contexts.
He himself solved the problem.
It's important to believe in yourself.
The president himself made that decision.
This is my own opinion.
Please solve the problem by yourself.
自身 attaches to a noun or pronoun to mean 'itself/oneself' (e.g. 彼自身), whereas 本人 stands alone as a noun meaning 'the person in question'.
Edo-period guardhouse
itself; himself; herself