Sōichi Mogami

Sōichi Mogami was a member of Border and Yūichi Jin's mentor.

History
Sōichi was a former Border Agent, and one of Border's founders. He also was Yūgo's rival. He used to be Jin's mentor. He used his life to make a Black Trigger, the same trigger which Jin formerly used.

Black Trigger Capture Arc
Yūma mentions him as the acquaintance his father had in Border. Rindō reveals that he died 5 years ago after creating Fūjin.