Sengoku Danshi Hana no Ran

From Which Scanlations:

With a boyfriend who's an idol on the rise and a wacky grandfather who has a penchant for inventing and Japanese history, Hana's life is crazy enough. Things get even more complicated when Hana runs into a burning building, trying to rescue her grandfather, and finds herself face-to-face with a man who seems to be a samurai from the past...