DxD: The Holy Knight!

Yasuhiro is known as the saint who embraces darkness throughout the entire world. As the older brother of Issei, he is the holy knight of the church and the madman who makes devils feel despair. In fact, he is a reincarnator from Earth. Having spent his childhood in Europe, he decided to visit Kuoh Academy for fun. Should the devils feel scared? -- "You mean, Lord Yasuhiro..." "He's worse than a devil." "Lord Yasuhiro is the gentlest man." "That bastard, didn't even spare my So-Tan." "I love him.." --- — Description from novelcodex.org