"Hitokiri" Shoujo, Koushaku Reijou no Goei ni Naru

Shurine has mastered the sword as a girl raised to serve as a bodyguard. However, she has been falsely accused of assassinating a client and is forced to go on the lam. Driven out of her homeland to a foreign land, Shurine meets Lutecia, a duke's daughter whose life is in danger, because she is embroiled in a dispute over the succession to the throne. Lutecia is attacked by an assassin, and Shurine makes a proposal.

(Source: Micro Magazine-sha, translated)