In the previous episode of Dr. Stone, Chrome and Kaseki invented the water wheel which allowed Senku to develop their Hydroelectric Power Plant. This allowed the Kingdom of Science, whose main objective was to create cell phones, the ability to shift away from manpower labor to focus on crafting other needs.
Finally harnessing the power of nature, Senku began to focus on creating boxes to store the electricity. He dubbed himself, Kaseki, and Chrome the “Spartan Crafts Club” as they started up their projects.
They crafted batteries, which eliminated the need for Kinro and Ginro to churn the energy wheel. They created gears, which freed up workers to prepare for the winter. Though they had a few roadblocks during their process they ultimately succeeded.
Kaseki admits to Senku that since he arrived at the village, life is better and more substantial. Besides a few villagers that do not enjoy the labor, the majority of the group are happy to help propel the Kingdom of Science forward.
Frost begins to form on the trees and the villagers are now wearing coats. During this time, the Spartan Crafts Club breaks ground on the light bulb.
Just as it begins to snow, Senku gathers the village around a tall tree for a test of their lights. He surprised them for Christmas and Ishigami Village enjoy their celebration.
Chrome received some new equipment and decides to go exploring while Kaseki and Senku continue evolving the light bulb to make it sufficient to support a cell phone. But they are unable to progress due to the type of materials they have. Senku accepts that they won’t be moving forward due to their limitations.
A Trio of Spelunking Buddies
New Years’ approaches and Chrome returns with copper and other rocks that he found. The group goes to the top of a hill to watch the sunrise.
The night before, Suika went through all of the rocks and found one that she thought would help. It turns out that the rock she kept was scheelite, an ultra rate gem used to make modern filaments and the “strongest metal in the universe”. This puts the Kingdom of Science back on track to create cell phones.
Senku prepares a group to go mining for more of this gem with Chrome and chooses Magma to accompany them as a “trio of spelunking buddies”.