Souichi Yakumo is second in command at TERRA, with the rank of Major. He often takes command when Kunugi is not present. Souichi is fond of Ayato and believes that regardless of whether or not Ayato is a Mulian, he is still himself and thus, should be looked at as an individual. Souichi is kind and friendly to everyone, and Megumi misinterprets this as a chance for a relationship. Soichi is oblivious to Megumi's feelings and starts seeing Kim. Despite being softspoken and friendly, Souichi is an able commanding officer.
SpoilerLater on in the series, Souichi is killed at the same time as Elvy by Ayato but is brought back after the world is tuned.