To Powerful Monster to Human Ninja! (Naruto Fanfic, Undertale cross over)

Sans told Frisk something that made Frisk not want to restart. Soon after he was lonely. No one to tell jokes... no one to run for it. Suddenly a portal open up under Sans. Then... you guess it... he failed down He wasn't in his normal body. He was a human! but he got used to it because he got turned into a human by A...