One of the most dedicated members of the investigation team. Little else is known of him. He remains mostly silent. This silence is marked when he refuses to answer Near's questions about the Japanese Investigative Team, even when he is clearly affected by the theories that Near was presenting to him. Later on, he is one of the first members who begins to warm to Near's theory that Light is Kira. He is also shown to be an excellent actor, showing an excitement and cheeriness completely opposite of his usual demeanor.
In the first arc, Mogi acts as Misa's manager (as Kankichi Moji) after Matsuda's faked death. Misa gives him the nickname of "Mochi," based on the alias.
In the second arc, Mello demands meeting Mogi in order to investigate about Kira, and tricks Mogi into meeting Near at the SPK headquarters. Mogi is then held hostage by Near until Aizawa arrives to rescue him.