Tatsumi, althougth a butler, is a good fighter of Kendo.
Relationship with Saints
Tatsumi was a good butler to Mitsumasa and Saori, but hated the orphans of Graad Foundation; he was a bad guy of the good size, and was a crusty with loyal servant; so, he never accepted slight against his bosses, and order the orphans to obeys Saoris Wishes. He always lashed the orphans of the foundation, so Ikki gets hatred of him, and want avenge on him.
How Saori is Athena (in the anime, only he knew about that), Tatsumi become a Athena's servant, and always tried protect her, and requires a lot of saints, rebuking them for their failure; but the teenager Saori and the old Mitsumasa never was callous with the suffering of the boys, and because this, made all the boys respect Mitsumasa (beating them) without their consent, Tatsumi was a rival of Kiki, and treated Kiki roughly.
He followed Saori in the 12 temples battle, and care of her when the arrow of Sagitta hurted her hearth. In Poseidon arc, he follow Saori to Julian's party, but in the anime, he stay with the minor bronze saints, and see the flood of Poseidon.
In Hades arc, tries stop Shun invasion of the Sanctuary, because Saori ordered that, and what Saori orders, is a law to Tatsumi.
In Omega, Tatsumi appears only in the begin of Mars and Pallas arc, and cares of Saori (injured by the darkness wound) and Kouga, but was a severe tutor for him.