The Lady's Training Session, with the Slimes

Suraimu-tachi to Ojōsama no Kunren (スライムたちとお嬢様の訓練)

Following Ryoma's advice that playing with magic is a good way to learn, Eliaria asks him to teach her how to play. Ryoma also asks Camil to teach him attack magic. Sebasu, the Jamils' butler, also teaches Ryoma advanced teleportation and storage magic. The next day, the Jamil family and their soldiers visit a mine overrun by monsters so Eliria can learn. After encountering cave mantises, Eliaria uses her magic to kill them, while Ryoma uses his new warrior skills. Eliaria discovers and catches a rare metal slime and gives it to Ryoma as a gift. 

Ryoma realizes that the mine can be reopened by using magic to extract the tiny traces of iron left in the soil, delighting Duke Jamil. Reinbach introduces Ryoma to Serge Morgan, a trader, who is delighted to buy and sell Ryoma's creations, making Ryoma very wealthy, though Ryoma insists on remaining anonymous, fearing the attention he would receive if anyone nefarious discovered he can use real alchemy. Reinhart finishes his investigation and has the embezzlers arrested. Having received a request from Duke Jamil, Reinhart decides to send Ryoma and other adventurers to clear the monsters from the mines.