Ok. I have the two units that have cancel affinity, Innes and Mathilda, both 5 starred. Should i inherit one onto my Halloween Sakura?

abso-freakin-lutely! I did it to mine. Best call I ever made. Now there is no mage that can beat her(She's got summoner support, +5 merge and DD seal, so even Reinhardt fails)

Use mathilda.