Help

Hi peeps, I'm looking for a particular manga which I read quite a long time ago and don't really remember much. But I do rememver that the protagonist is a male assassin, top in his field, whi accidentally warps to a different world. In that world, he enrolls in a school that categorizes its students into 3 groups. Knight, magic(if I'm not wrong) and mecha(piloting robots). Apparently he managed to make a name for himself in that world and most people started calling his secret identity Silver Knight or something along those lines. That's about all I can remember, would really appreciate it if there is someone who knows this manga:)