Tadashi Yamamori serves as Hiroshi Umino's steadfast companion throughout their shared story. He stands by Hiroshi during their time on an unfinished ocean city structure when it suffers a devastating attack and collapses, plunging both characters into the sea. Rescued but afflicted with complete memory loss regarding the incident and their rescue, Tadashi and Hiroshi recover together in the hospital. Following discharge, they return to their shared residence. Police later storm their apartment; Hiroshi is arrested for interrogation while Tadashi remains present during the intrusion, visibly bewildered by the unfolding events. Beyond these specific occurrences, no additional narrative development, background information, or expanded role for Tadashi Yamamori exists within documented official media.