Using step up feat on moving npc

Question

I'm playing pathfinder with the core rulebook only for my campaign. I wanted to take the step up feat for my monk, and I was wondering if it applies to every movement like a full movement/withdraw or specifically to the 5-foot / 1,5 meters step.

Step Up (Combat)

You can close the distance when a foe tries to move away.

Prerequisite: Base attack bonus +1.

Benefit: Whenever an adjacent foe attempts to take a 5-foot step away from you, you may also make a 5-foot step as an immediate action so long as you end up adjacent to the foe that triggered this ability. If you take this step, you cannot take a 5-foot step during your next turn. If you take an action to move during your next turn, subtract 5 feet from your total movement.

The description says "5-foot", but how can my pg be aware if the opponent is moving for a step, a full movement or even withdrawing? And if I'd have the following step feat (which I cannot take, but that's a horse of another color) I'd be able to follow for 10 feet. If this applies to every kind of movement, it makes a good combo with the feat Stand still.

Stand Still (Combat)

You can stop foes that try to move past you.

Prerequisites: Combat Reflexes.

Benefit: When a foe provokes an attack of opportunity due to moving through your adjacent squares, you can make a combat maneuver check as your attack of opportunity. If successful, the enemy cannot move for the rest of his turn. An enemy can still take the rest of his action, but cannot move. This feat also applies to any creature that attempts to move from a square that is adjacent to you if such movement provokes an attack of opportunity.

In this way, even if a npc withdraws, it's possible to vain his immunity from an attack of opportunity during the first step by following him, and then, when he provokes a second attack, stop him.

What do you think? Is this reasonable? Thanks!

Answer 1

The feat Step Up triggers only versus a 5-ft. Step

Following the link, you'll see that the 5-ft. step is a specific action. Although other actions allow movement of only 5 ft. these don't meet the feat Step Up's conditions as moving only 5 ft. is different from taking a 5-ft. step.

The game provides no rationale

It's unclear in the rules how the character can differentiate between a 5 ft. step and, for example, taking the Withdraw action and only taking 5 ft. of movement, but somehow the character can. The game abstracts much of the character's ability to read the battlefield. If a rationale is necessary to maintain immersion, just say 5-ft. step, because it behaves differently mechanically anyway, obviously looks different to the character, and be done.

Answer 2

I think most of you are missing the true intention of this feat, and it's presentation in the APG only makes things worse. (I think!)

Consulting the rules on immediate actions, using the feat is a swift action but can be performed by the player even on another's turn… A swift action implies that only one swift action can be performed during a single turn. My point is that Step Up in it's bare form can only be used once per turn using a character's swift action "slot" for the turn.

Then comes Following Step, and its description strongly implies multiple uses of the feat Step Up:

You can repeatedly close the distance when foes try to move away, without impeding your normal movement. When using the Step Up feat to follow an adjacent foe, you may move up to 10 feet.

(Emphasis mine.) So now multiple enemies can be subject to the Step Up feat, and it doesn't cost the stepper any movement on its turn. But it is still multiple uses of the Step Up feat. How many? Two for a total of 10 ft. Why? The Step Up feat limits the use of this feat to 5 ft. and Following step (as the name implies) increases this distance to 10 ft. Hence Following Step can trigger twice off Step Up, moving 5 ft. each time up to 10 ft. total, and it doesn't affect the stepper's movement. This makes the feat fairly powerful.

The feat after that allows the stepper to the foe he follows: Step up and Strike. This feat also implies that either the stepper's using the Step Up feat or the Following Step feat to smash foes. If Step Up is used only once, it will be the Step Up feat that triggers, but if the stepper uses the Following Step a second time, Step Up and Strike triggers off of Following Step.

I've reached these conclusions based on the feat's descriptions, and for me the whole thing makes sense.