Shinsengumi Imon Peace Maker

When childhood innocence gives way to a blinding thirst for revenge, is it worth the price of one's humanity? Tetsunosuke and Tatsunosuke are the sons of a diplomat who sought to bring peace and prosperity to Japan during the early Meiji Restoration. But when their parents are murdered before their very eyes, Tetsu seeks to join the Shinsengumi, the unofficial police who are capable of the same brutality as his parents' murderers. Wading through a sea of espionage, deception and bloodshed, the young boy must choose: should he take a step on the path to becoming a demon... or give up his rage and transform into the ultimate Peacemaker?

(Source: Tokyopop)

Included one-shot:
Volume 6: Wagamama Tenshi no Sodatekata.