The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat, Vol. 4 (light novel) - Reia Reia, Rui Tsukiyo

Unexpected Allies... and Enemies​During a party in the royal capital, Lugh runs into Mina, the mysterious and flirtatious snake demon. Evidently, she’s already infiltrated human society, but not to take it over. She’s not too thrilled about seeing the Demon King revived and wishes to help Lugh prevent that from happening...or does she? Mina seems to have her hooks in many different important people: nobles, princes, and even Lugh’s friends. Will this wolf in sheep’s clothing manage to turn classmates against one another?