The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat, Vol. 3 (manga)

Face-to-face with his target at last…
Lugh took his latest mission with confidence, but when he barely manages to stop the assault on Count Viekone’s castle, he realizes something. As they are, his skills aren’t going to cut it against the hero—his true target, who’s…also going to be studying at the same academy as him?! Can Lugh use this opportunity to turn the odds in his favor…?