Saburō is an Afghan Hound owned by Jirō Tanaka and a companion to the staff of Monthly Moso Science magazine. He displays uncanny human-like intelligence, performing complex actions such as dancing and sumo wrestling despite his canine form preventing speech. His true identity is eventually unveiled as a Motarian—an ancient entity originating from the sunken Mo Continent—with the implication that Saburō possessed awareness of this heritage long before the other characters discovered it.

When transforming into his Motarian state, Saburō initially manifests as a humanoid figure adorned in attire reminiscent of ancient Roman or Greek styles, wielding a harp. This form signifies his past role as a bard on the Mo Continent. His ultimate, primordial form is later exposed during the climax: a colossal ancient bird.

In the final confrontation to halt humanity's eradication, Saburō delivers a vital clue by playing a culturally significant Motarian melody on his harp. This specific song contains encoded instructions crucial for deactivating the doomsday device, Ra Mo, and triggering the Mo Continent's submersion. Though initially observing passively as the continent collapses, Saburō ultimately shifts into his gigantic avian shape to intervene directly.

Following the Mo Continent's destruction, Saburō, like all surviving Motarians, permanently loses his transformative abilities, remaining henceforth in his original canine form.