Shin Sangoku Shimai

High school student Shuuichi Mizuki and his sister-in-law Nanami are summoned as Liu Bei and Zhang Fei to the world of Romance of the Three Kingdoms!? Furthermore, his sister who has been separated from him since birth, Yukino, is also summoned as Guan Yu. In order to ensure his sisters' survival, Shuuichi fights by making use of his Three Kingdoms knowledge and his ability as a hero!

(Source: Kadokawa, translated)