Hirooka functions as the Momoi family’s steadfast protector, remaining perpetually vigilant at Momomi Momoi and Momokichi Momoi’s sides. Renowned as the family’s most formidable operative, his unflappable composure and precision under pressure solidify his reputation. Though his inscrutable demeanor and emotional distance cloak his intentions, faint traces of dissent surface in his guarded reactions to Momokichi’s leadership tactics with the Peach Twisters and Momomi’s recklessness.

Behind his dutiful facade, Hirooka masterminds a calculated campaign to destabilize the family’s authority. As security chief, he exploits the Danger Service Agency through strategic deception, aligning with them to dismantle the Momois’ empire. His intricate betrayal includes orchestrating Momokichi’s assassination under their banner and engineering a lethal clash between Momomi and her adversaries.

The final phase of his plan unfolds during a rigged hostage exchange, where he maneuvers to eradicate all opposition after the Momois’ collapse. Unbeknownst to him, the Danger Service Agency anticipates his treachery, countering his ambush with a robotic Momokichi duplicate equipped with a self-destruct mechanism that ensures his demise. His story concludes within this documented chain of events.