Visual Novel Version

Bachō's cousin. A new character in the sequel, Shin Koihime Musō. Despite being younger than Bachō, she has no issues being around men. In fact she often teases Bachō about the latter's issues with men, sometimes by putting her into embarrassing situations, like bringing her to see Kazuto while he's bathing in a river causing Bachō to freak out. She also likes Kazuto, and is aggressive in pursuing him, going as far as to lead him out to a forest (on the pretense that Bachō was kidnapped), knock him unconscious, and have her way with him.

Anime Version

Batai first appears in the 11th episode of Shin Koihime Musō to train under her cousin Bachō and made friends with Riri at Touka village. Due to Bachō harsh training methods, Batai gets her revenge on her by tricking her to drink a giant gourd of water and not allowing her to use the bathroom by sundown or faced being called a bed wetter. In Otome Tairan, Batai snuck-out so she could go on an adventure with Chouhi and Ryuubi. She later meets Gien, who she develops a rivalry with.

(wikipedia.org)