There's a subset of fiction where someone can be 'just that good' that things seem like magic. Anime can have it, but you also see it in stuff like the smoke knights in Girl Genius where they are effectively invisible and can steal/replace-with-something-else your hostage or the weapon you are holding without you noticing, etc. Likewise combatants can move from safe distance to right up in your face (with a knife in your ribs) in a literal eyeblink. In D&D terms, it wouldn't be magic, but could replicate many* magic abilities short of flying or dimensional travel (and certainly could be presented in a similar fashion to spells**). A line attack wouldn't be magic, they are just charging through an area taking a slice at every opponent in turn. Teleporting is just moving such that no one notices you between points A and B. And similar.
*especially if you take a rather liberal interpretation of 'realism' for things like running up a wall, what can be accomplished in an eye-blink, and so on.
**and honestly magic, psionics, Bo9S maneuvers, and various feats are mechanically all just modular rule exception text blocks.