What skills/attacks classify as Unsheathed?

I'm curious which attacks classify as an Unsheath attack. Going by animations, nearly all of our attacks look like unsheath attacks, but that doesn't necessarily mean they are. Does anyone know which ones are or aren't?

Also, is the unsheath attack modifier a straight % damage increase to unsheath attacks?

 

All of class can done with first attack
For skill :
1. DW can do as after cast skill shadow steps, it only first normal attack.
2. Katana have plenty, issei, hasso, zattei, lot of skill using unsheathed here.
3. All class need skill shukuchi to dash forward enemy. After shukuchi effect, it will be unsheathed first, then normal. To do it, go out of range and press attack into enemy.
4. Make sure your dodge high and even evasions, all attack automatically turned into unsheathed when you triggered evasions.