Takeo is the brother Maseo Yamashiro, Katana's Husband, who became jealous when Katana picked Maseo over him. He trained for years so he could one day have his revenge. He broke into their house, setting it on fire, and killed Maseo and Katana's two children. Years later, He snuck into the house where Katana and Halo were staying and a fight ensued. Takeo came out on top,taking the soultaker with him, and leaving Katana and Halo unconscious. He used Soultaker to summon ancient warriors that the soultaker had slew including Maseo. They then fought with the Outsiders, winning and making them retreat. He and his warriors were attacked by the outsiders and were all killed.
Takeo Yamashiro first appeared in Batman and the Outsiders #9, created by writer Mike W. Barr and artist Jim Aparo.
Major Story Arcs
Outsiders: Five of a Kind
When Takeo was killed by the Soultaker, his soul was trapped in Fukumaden, the realm within Soultaker. Somehow he rouse to power and became Emperor Takeo. He started a slave trade, which didn't sit well with the other souls trapped. One such soul,Captain Haruta started an uprising to over throw Takeo. Takeo then knowing to defeat Haruta he's need to take control/kill Katana. So he sent assassins after her knowing she'd come after him in Fukumaden.
When Katana fell for the trap and sent her soul to Fukumaden, Takeo sent Battleaxe to destroy her physical body. But Battleaxe failed and Katana was returned to her body and Takeo was defeated by Haruta, for now.
Takeo shows up in the rebooted universe under the alias "Sickle", though much of his back story remains the same. He is shown to be a member of the Sword Clan.
Batman: The Brave and the Bold
A version of Takeo appears in the animated series, who in this version is Katana's brother. In a Pyscho-Pirate induced hallucination in the episode "Inside the Outsiders", Takeo is shown to want the Soultaker sword for himself after Katana tried to hide it from him.