expression, godan verb (iku/yuku class)
advance unobstructed; move freely like a heavenly horse
Idiomatic expression evoking the image of a celestial horse galloping through the sky without hindrance. Used to describe unimpeded progress or free, unconstrained movement.
彼の想像力は天馬空を行くがごとく、何にも縛られない。
His imagination advances unobstructed, like a heavenly horse galloping through the sky, bound by nothing.
The expression derives from classical Chinese imagery of a celestial horse (天馬) galloping freely across the sky (空を行く), symbolizing unhindered movement. The exact historical origin is uncertain, but it is used idiomatically in Japanese to convey unimpeded progress.