So, as we all know,
Shijin Spiral + Penta Thrust = Nothing
Penta Thrust + Shijin Spiral = Nothing

But Council, has realized, that Tachi:Kasha may not SC with either of those as well.

So first, I looked at the Skill chain properties of Kasha, and confirmed, it shouldn’t. We then did live test on random amerats, and was confirmed again: Does not SC
Shijin Spiral + Kasha = Nothing
Kasha + Shijin Spiral = Nothing
Penta Thrust + Kasha = Nothing
Kasha + Penta Thrust = Nothing.

So this led me to determine even further, “Is there any more weapon skills that would not SC?

Turns out: YES! (can skip to the bottom for final results)

Using these charts:
Level 1
Level 2
Level 3

Let’s look at the Properties of those 3 known SC-less weapon skills:
Shijin is aligned with Fusion and Reverberation
Penta is aligned with Compression
Kasha is aligned with Fusion and Compression

Using those charts:
Fusion + compression = nothing
compression + Fusion = nothing
reverberation + fusion = nothing
reverberation + compression = nothing
fusion + reverberation = nothing
compression + reverberation = nothing

putting together that, and the findings on Kasha working in the set of no SC weapon skills:
Any weapon skill with compression, reverberation and/or Fusion will NOT skill chain with each other.

The final result of all this, the list of Weapon skills that should not Skill chain (at least, theoretically, except the 3 confirmed ones):

1H Axe:
Decimation (aligned with Fusion and Reverberation)

Great Axe:
Keen Edge (aligned with Compression)
Upheaval (aligned with Fusion and Compression)

Ranged
Arching Arrow (aligned with Fusion)

Club
Brainshaker (aligned with reverberation) (NOTE: Assuming it counts as physical)
Hexa Strike (aligned with Fusion)

Dagger
Shadowstitch (aligned with reverberation) (NOTE: Assuming it counts as physical)
Mandalic Stab (aligned with Fusion and Compression)

H2H
One Inch Punch (aligned with Compression)
Shijin Spiral (aligned with Fusion and Reverberation)

Katana
Blade:Teki (aligned with reverberation)

Great Katana
Tachi:Kasha (aligned with Fusion and Compression)

Marksmenship
Heavy Shot (aligned with Fusion)
Last Stand (aligned with Fusion and Reverberation)

Polearm
Penta Thrust (aligned with Compression)
Wheeling Thrust (aligned with Fusion)

Scythe
Insurgency (aligned with Fusion and Compression)

Staff
None. All the ones with correct alignments, are Elemental WS…..

1H Sword
lol Atonement (aligned with Fusion and reverberation)
and maybe Sanguine Blade, since it is not aligned with anything.

Great Sword
Shockwave (aligned with Reverberation)

and for shits/giggles:
Bloodpacts
Camisado (aligned with compression)
Moonlit charge (aligned with compression)
Barracuda dive (aligned with reverberation)
rock buster (aligned with reverberation)
double punch (aligned with compression)

Automaton (though…very problematic, would require specific maneuvers up only during use)
Cannibal Blade (aligned with compression)

Sucky part is, as more and more WS's get confirmed to not skill chain, the tests will require more and more testing with the others lol.

As we confirm more, though, I will post replies with the confirmed weapon skills.

enjoy :D !!!