Heike Monogatari Yoru-kun no Hanashi

The time is the Reiwa Era. Childhood friends Sara Futagi and Yoru Haruno are going through their usual morning routine... but then ......! Somehow, they are suddenly transported into the world of the Tale of the Heike, where Yoru-kun has become the daughter of Taira no Kiyomori, while Sara-san has taken over the body of Minamoto no Yoshitsune!

(Source: Comic Beam, translated)