Oinochi Choudai!

Ruri is a clumsy ninja who fails almost every mission. But Ruri remains undaunted, all for the sake of her ailing younger sister, Murasaki. One day, Ruri learns that there is a 100,000-ryo bounty on the head of Tokuyama Tenryori, the shogun of Edo, who lives in an impregnable castle full of traps and sorcery. The battle for Edo Castle is about to begin!

(Source: ComicWalker, translated)