第 3 集: Nagi和Ruri探索大學實驗室，發現了一塊神秘的鉍晶體以及一張古老的地圖。
2025年7月20日 播出
Nagi brings Ruri to her messy graduate lab at the university, where Ruri meets Nagi's colleague Yoko. Nagi has published a paper on the unusual pyrite crystal Ruri found and listed Ruri as a co-author. In tidying up the lab, Ruri finds an otherworldly-looking bismuth crystal. Nagi shows her how it was made. Ruri also finds an old topographic map, valuable because it shows a mine not depicted on newer maps. The three girls travel to investigate. A magnet helps identify iron ore in the tailing pile. Falling into a collapsed section of tunnel, they must traverse more tunnels to escape. Nagi's ultraviolet flashlight reveals a galaxy of fluorite crystals not previously recorded. Nagi encourages Yoko to lead a study on them. (Source: Wikipedia)