Dominic mentors Renton Thurston and Eureka during their childhood in Warsaw, serving as their teacher and caretaker. He imparts knowledge of natural phenomena, including the rare snow moon flower, explaining its mythical properties: the ability to grant wishes and display rainbow colors when dreams are fulfilled. Before departing on a military assignment, he gifts the children snow moon flower seeds, suggesting they could help realize their dreams.

Tragically, Dominic dies one week after his departure during a failed military experiment aimed at developing weaponry against the EIZO aliens; his death occurs offscreen. This loss leaves Renton and Eureka without his guidance, compounding their isolation when soldiers later take Eureka.

Dominic reappears posthumously as a spiritual manifestation during Renton's moments of doubt. In this form, he advises Renton to prioritize emotional conviction over rational thought and urges him not to relinquish his feelings for Eureka, reinforcing his enduring influence as a guiding presence beyond death.

The film's conclusion notes his relationship with Anemone, as their spirits reunite in the afterlife following Anemone's own death, implying a connection transcending their mortal experiences and signifying narrative closure for both characters.