Show Yourself!
Ever since August transmigrated to this world, he had been working hard to improve his knowledge base about Sorcery and other supernatural elements of the world. Compared to other Apprentice Sorcerers, who normally only had time to complete missions and focus on elevating their power as quickly as possible, August was more productive. He made use of Rhea's computational abilities to collect as many pieces of information he could have access to from the library of the magic tower and hence he was more knowledgeable about the Sorcery and other fields than his peers. This meant that he knew about demonic energy.