Takuya Shirakawa, one of three middle school friends bound by their obsession with a mysterious tower across the Tsugaru Strait, carries a name echoing his narrative purpose: "white river" in his surname and a given name blending "expand, open, support" with "to be, also," mirroring themes of growth and duality.

As teenagers, he and Hiroki Fujisawa labor at a munitions factory to fund an aircraft project, determined to honor their pact to fly their friend Sayuri Sawatari to the tower. The trio fractures when Sayuri vanishes, shattering their shared mission.

Three years later, Takuya studies physics at a U.S.-allied facility exploring the tower’s ties to parallel universes, analyzing its capacity to swap matter with alternate-reality counterparts. His research intersects with the Uilta Liberation Front, a paramilitary faction led by former employer Mr. Okabe aiming to destroy the tower to reunify Japan. Collaborating with colleagues like Maki Kasahara, he navigates political intrigue while wrestling with unresolved grief over Sayuri’s absence, adopting a reckless, emotionally guarded persona that strains near-relationships.

Reuniting with Hiroki reignites old tensions, culminating in a brutal ultimatum: save Sayuri or avert global disaster. Though initially adversarial, Takuya later assists Hiroki in finishing their aircraft, choosing childhood vows over geopolitical consequences.

The novel adaptation delves deeper into his moral conflicts with the Uilta group and the ethical ambiguities of his work. During the climax, programming the aircraft’s systems and surrendering his seat to Hiroki mark a pivot from detachment to redemption, driven by a need to heal broken bonds and reclaim their shared childhood purpose.

His portrayal remains confined to the original film and novel, with no extended media elaborations documented.