The Age of Energy.
Senku and Ishigami Village begin work on the cell phone, planning to complete its construction by spring. In order to manufacture gold filaments for wiring, Senku creates a cotton candy machine to test with sugar. Senku brings cotton candy to Homura, who has been spying on the Kingdom of Science. After running into imperfections making filaments, Senku develops a gear train for the cotton candy machine, inspiring Chrome to construct a waterwheel with Kaseki.