The Old Astronomer is grandfather to a boy named Yuri, sharing residence with him in a laboratory-like structure on an island within a lake. Their home includes an attached observatory for celestial observation and houses an indoor rainforest sheltering unique flora and fauna—among them luminescent tomatoes and lemur-like creatures.

He routinely prepares meals for Yuri and himself, though occasional mishaps like burnt dinners occur. His astronomical expertise surfaces when he detects an anomaly: an extra star in Ursa Minor and the constellation’s shift into a fish-like shape. Recognizing the threat to the Milky Way’s stability, he embarks with Yuri to investigate.

Navigating a surreal oceanic sky merging with space, he rows their boat past submerged terrestrial elements—towns, railways, forests—below the water’s surface. He interacts calmly with anthropomorphic aspects of their world, such as reassuring a sentient, walking building distressed by vanishing stars. Familiar with a wizard dwelling near star-forging stone giants, he seeks counsel directly. After the wizard reveals a giant fish consumes celestial bodies, the Old Astronomer supports Yuri’s use of a magically forged harpoon against the creature.

He maintains methodical composure throughout encounters—including a damaged robot and traversal toward the M81 galaxy—reflecting his acceptance of the world’s inherent wonders and dangers. His relationship with Yuri centers on quiet guidance and shared purpose. Following their mission’s resolution, he returns to domestic routines, enjoying a drink from a large liquor jug, reaffirming his stabilizing presence in their isolated, observatory-centered existence.