In the past, when he belonged to the "Sanada Juuyuushi", Shindara was called Sarutobi Sasuke. After being informed of Yukimura's premature death and his failure to seize hold of the country through the Taishirou Tokito's predictions, he left the Sanada and joined the Mibu to spy on them and to save Yukimura's life when the time comes. He is called the immortal one because Hishigi modified his body so he can regenerate instantaneously. He faces Yukimura and loses, but his motivation behind his betrayal is revealed. Later, he saves Sasuke from death and dies from mortal wounds beyond the healing capacity of his regeneration.  After Bikara died, Shindara looked after Antera and acted as her parent keeping her at his side at all times.

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)