Kootetsu no Hana

Summary from Saigo no Shou:

During the turbulent Bakumatsu, a group defends the capital city of Kyoto and the Tokugawa Bakufu: the Shinsengumi. The man known as a “demon” throughout the group: Vice Commander Hijikata Toshizo. The top swordsman in the group, one who looks up to Hijikata: Okita Souji. But deep inside Okita’s heart lies an Okita who hates Hijikata with a passion… and that Okita is about to awake!!

Creator: KANNO Aya
Length: 1 volume
Scanlation status: Ongoing
Genre: Historical, Shoujo