The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat, Vol. 2 (light novel) - Reia Reia, Rui Tsukiyo

The Assassin Meets the Hero​Lugh, Dia, and Tarte enroll in the most elite academy in the Alvanian Kingdom. On the surface, the group is there to learn how to be knights, but Lugh’s real goal is to get close to the hero he’s been tasked with eliminating. However, Lugh winds up getting more familiar with the hero than first intended, and he learns that the prophesized savior’s power comes at a steep price. Being a hero isn’t easy, and when trouble strikes, will the assassin have to save the one he’s supposed to kill?