Mukan no Kishi, Youjo ni Tensei suru

A professional shogi player in his 40s, without a title, is shocked after losing to a young genius shogi player known as the "Demon King" in a Meijin match and is reincarnated as a little girl named Sakura. Sakura has a twin sister named "Ouka" by her side. Sakura's thirst for shogi never ceases and she vows to get revenge on the "Demon King," discovering Ouka's talent! (Source: Akita Shoten, translated)