Both spellings are entirely correct, but their usage depends heavily on the specific language, cultural origin, or romanization system being utilized. "Toya" is a standard Hepburn romanization frequently used in Western contexts, while "Touya" represents a more precise literal transliteration of the Japanese long vowel sound (とうや). In the context of anime and manga characters like the one from My Hero Academia, both spellings are frequently encountered by international fans, though official English translations and subtitled releases often lean toward Touya to mirror the Japanese syllabic length accurately.