Even though she is just a child, Santera has a powerful ability. She emits a powder that melts whoever comes into contact with it. Her true form was released by a Mibu serum in the battle with Akari: a beautiful butterfly woman who was able to burn anything in her path. Because of her powder, she could not have a relationship with anyone in her life, so Nobunaga adopted her as one of his Juunishinshou. After she had a fight with Akari, she and Akari became firm friends. She left the Mibu Clan along with Antera because she had someone she could call "friend" in her heart. 

At the dawn of the 17th century, at the end of the era of civil wars, in a world of chaos, the epic Battle of Sekigahara was joined. One man emerged from the largest battle ever fought on Japanese soil; a terrible warrior of unspeakable power, he was nicknamed 'the unconquerable.' 
Kyoshiro is a peaceful medicine peddler who harbors the soul of an assassin. He accompanies a young bounty hunter across Japan in search of a murderer and on a quest to discover the terrible secret of his own identity. (Source: Tokyopop) 
 
Volume 38 contains the side story "'Michi' no Tochuu" (「道」の途中).

In the year 1600, during the battle of Sekigahara, warriors Kyoshiro Mibu and "Demon Eyes" Kyo - the legendary slayer of a thousand men - engaged in fierce combat. Both men disappeared when a meteor crashed in the battlegrounds. Four years later, Kyoshiro is spotted on a rural highway, acting as a traveling medicine salesman. He is captured by the female bounty hunter Yuya Shiina when she discovers that deep inside him is the dormant personality of "Demon Eyes" Kyo himself.
 
(Source: Anime News Network)