Stone Road (
The villagers discuss theories on the newcomer, assuming anything from being an ex-banished member to an alien to a revived statue. Kokuyo is informed by Jasper and Turquoise that the outsider was led to their village by his daughter, Kohaku. He becomes angry, but is distracted from it when Ruri collapses into a fit of coughing.
The science trio is determined to save Ruri, and Senku explains their options. They'll need an antibiotic, however Senku has no way of knowing what she has because he can't check her blood work. Their options are to either get lucky with a super powerful strain of penicillin, or making a sulfa drug using rocks. Because it's almost impossible to get lucky with the former, Senku says they'll choose the rock route.
That evening, Senku tells Chrome and Kohaku about science of the old world. They learn that the earth is rotating. Senku points out the North Star, but according to Kohaku it's not perfectly true north. Senku realizes that he got lost on his way to Hakone because the planet's axis has titled more over the 3,700 years. He asks how Chrome and Kohaku knew where north was, and Chrome shows Senku a small stone he's discovered, which always points north when floated on a leaf. Senku is excited, Chrome has discovered a natural magnet and reinvented the compass. With this resource, Senku tells them they'll begin collecting iron sand.
Characters in Order of Appearance
- The villagers discuss Senku's appearance.
- Senku explains the plan to save Ruri using the sulfa drug.
- The Earth's tilt has changed over 3,700 years and the stars are no longer in the same place.
- Chrome reinvented the compass.