21화: 센쿠가 철 생산을 기계화하고 겨울 준비를 위해 텅스텐으로 전구를 개발한다.

21

With electricity now available, Senku mechanizes the ironmaking process, freeing up the villagers to prepare for winter. Meanwhile, Senku, Chrome, and Kaseki begin developing light bulbs, allowing them to celebrate Christmas by decorating a tree. Chrome uses the new invention to explore deeper in caves, where he finds a host of new minerals. Senku and Kaseki attempt to create a vacuum tube, but they cannot find a filament that can withstand the heat. During a New Year's sunrise, Senku receives inspiration from Suika and realizes tungsten is the solution and employs himself, Chrome, and Magma on a spelunking expedition. (Source: Wikipedia)