Nice... An Idea: Nobita as Shirou Emiya A massive fire broke out in the City they live in that killed a large number of people (Including Nobita's Parents), Nobita survived the Fire but due to Head Injury, Trauma, and Curses Nobita lost all memories. He was saved from the fire by Kiritsugu Emiya (The Magus Killer) and was ultimately adopted by him and given the name, Shirou Emiya (As Nobita didn't remember his). If you do this idea and do a pairing... can it be Saber.