Dr. Stone › Saison 1 Dr. Stone : Stone World

Chapter 7 — Episode 7

First, the episode opens with Kohaku formally introducing herself to Senku and offering to cooperate with him, clarifying that her admiration is not romantic but based on respect for his character. She reveals she sleeps with her sword drawn out of habit, and the two agree to work together against Tsukasa. Kohaku proposes leading Senku to potential allies, explaining that her older sister Ruri is ill and needs hot spring water for therapy, which Kohaku has been hauling daily as both treatment and personal training. Then, on their journey, Senku builds a simple wheeled cart using the pulley from the previous day to help transport the heavy water jug, demonstrating how one invention builds upon another. They arrive at a primitive village where they encounter Chrome, a self-proclaimed "sorcerer" who challenges Senku to a sorcery duel. Chrome performs a colored flame display he calls the "Rainbow Bridge" by throwing salt, copper crystals, and sulfur into a fire, but Senku immediately identifies it as ordinary flame coloration reactions. Chrome then produces a sulfur ball static electricity generator — a device Senku recognizes as a 17th-century invention — impressing Senku, who discovers that Chrome independently collected minerals, plants, and scientific materials entirely on his own. Finally, Senku visits Ruri, a priestess and Kohaku's ailing older sister, and learns the full gravity of her condition. Chrome reveals he became a sorcerer specifically to find a cure for Ruri's illness. Senku then tells Chrome the full truth about the Stone World and humanity's 3,700-year petrification, which moves Chrome to tears. Inspired and determined, Chrome pledges to join Senku in building a Kingdom of Science, and Senku declares their goal: to create antibiotics —