Tachihara leads the communist terrorist group Red May, orchestrating infrastructure attacks to destabilize Japan's political and economic systems for a communist revolution. Unbeknownst to him, Governor Maisaka covertly manipulates Red May’s operations to fuel illegal arms trafficking, profiting from the engineered chaos.

After his capture by the Special Security Force, Tachihara withstands extensive torture without yielding critical intelligence. His resolve shatters upon learning that psychic vigilantes called Hunters annihilated Red May. This defeat triggers his confession, exposing Maisaka’s conspiracy and the incriminating H-File.

During a high-security transfer guarded by agents Hacker and Peace, the telekinetic Hunter Lucifer intercepts them. Severely weakened from interrogation, Tachihara cannot evade her. Lucifer crushes him against a bridge support beam with her powers, killing him in custody and eliminating him as a liability to Maisaka.

Tachihara’s pre-Red May background remains undisclosed. His character shows no ideological evolution, functioning solely as a committed terrorist leader who propels the plot. His portrayal remains consistent across anime OVA and manga adaptations.