I think about this story so often. Loved it!
Two men meet by chance but their fates are bound together forever after. A confident, highly skilled sword fighter gets surprise help from the King of the land who then orders him to become his personal bodyguard. The King is not only a skilled fighter himself but he also doesn't trust even those close to him. The man is suspicious of becoming a bodyguard for such a man but over time, their trust in each other grows.
Shirogane no Ou