Remembered a scene I saw on youtube years ago, for some reason wanna try and find it again. Sorry if I sound like I'm crazy

Ok so lady is fighting bandits or whatever in a town, guy shows up to help, he transforms (I think) into a different guy. he's got white hair after changing, calls himself dragon or whatever. Throws a punch named "phoenix", she falls in love with him (Again, sorry if I sound crazy, I just randomly had this memory pop back into my head and have no way of finding it)