Usage patterns
本来の〈物〉the original/true form of something
He returned to his true self.
本来〜べきだshould originally/properly do something
Properly speaking, I should be the one to apologize.
〈事〉は本来〈形容詞〉something is inherently/by nature [adjective]
This rule is supposed to be simple by nature.
Expressions
本来ならby all rights; properly speaking; normally 本来であればby all rights; properly speaking; legally speaking 本来から言えばby all rights; properly speaking; legally speaking