in demi?

do you have to be using the awakening of light skill for the effect to take place?

Seriously? Read the category page. God.

Wasn't this the one treasure where it also worked outside Demi, that's how I remember it...

Wave Sweeper works regardless of whether or not you use awakening of light.

Waitwaitwait. There are treasures that don't require awakening? Whaaaat? Eh.

Wave Sweeper works at all times. I tested it on KR server many times. If you're running and you equip a high grade wave sweeper your char will speed up, as will the animation. Its effect stays till you take it off.