ChuSinGura 46+1 Kanade Hon-ChuuShinGura-hen (2011)

This is a sound novel by Rain Dog depicting the events of Chushingura, where 47 ronin sought revenge for the death of their master, Asano. The twist here is the protagonist Suguha falls into a time slip and ends up in the Edo period, and the ronin are mostly girls.