King of the Stone World.
Senku and Taiju prepare enough revival fluid to free one person from stone, with Taiju choosing Yuzuriha to be first subject. However, they are suddenly chased by a group of hungry lions, leading them to instead revive the strongest fighter in their town, Tsukasa Shishio, to fight them off. Tsukasa killed the male lion and skins it to add to his attire. As Tsukasa proves to be a valuable hunter, providing food for the trio, Senku assigns Taiju with harvesting seashells and grind them into calcium carbonate as a first step towards advancing civilization...