His semblance is the ability to summon slashing storms. Just the slashing storms and slash extensions. That's where the ranged capabilities come from. It does have a delay so it isn't difficult to dodge unless you're already doing something or he manages to hide it or read your next move. You'll be able to tell when silver lines start appearing.

The katana is an ordinary katana with reinforcements. In the hands of someone who cannot channel aura, it is entirely ordinary. It is simply receptive to aura, and will increase sharpness, with enough it can slice through aura-made barriers or certain semblance defenses too. Anyone who can channel aura would be able to make use of that function easily. So yeah, basically, very sharp, receptive to aura for more power.

His aura ability is the flow. First of all, its not Semblance. Sorry its placed there, but its just the way he uses his aura, and took the place of his semblance for his first year since he had no semblance for the first year.

Why it works is that rather than using his aura statically like simple shield, strong punches, etc. He runs it through his body like a secondary flow of blood or nerves, using it to enhance both movement and reaction timing. Of course because of how it works, using it as a shield to avoid major damage when he is struck costs him more than aura like anyone else, but also costs him some of that accumulated aura, making him a little slower. Although it comes with the ability to continually use incredible feats of speed at a more sustained rate, and going beyond that with the super-tele-dashes.