Bachō's cousin in Shin Koihime†Musō, together they led the Ryōshū cavalry forces in an attempt to repel Sōsō's invasion. After Batō's suicide in response to Sōsō's victory, she follows Bachō and joins Shoku.
Unlike her cousin, she does not hold a grudge against Sōsō, especially after hearing how Sōsō buried Batō according to Ryōshū customs.
Batai first appears in the 11th episode of the second season to train under her cousin Bachō and made friends with Riri at Tōka village. Unlike Bachō, she is quite mischevious, pulling various pranks on her cousin and secretly leaving on long journeys despite being told to stay behind.
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.