Sekai Saikou no Ansatsusha, Isekai Kizoku ni Tensei Suru (Associated Names)

The eldest son of the assassin aristocrat Towerhades. The skill, experience, knowledge of the previous life, magic, all of which grows his power as an assassin. Excellent assassins pass through. He was usually admired as the ideal lord, and behind it wielded a blade as an assassin aristocrat.