Tensei Kizoku no Isekai Boukenroku: Jichou wo Shiranai Kamigami no Shito

Shiinya Kazuya died while saving young girls attacker, only to reincarnated into a world of swords and magic. It was a dream come true. He remembers his life and knowledge of Earth, now Cain von Silford, the third son of an aristocrats.