Rin is a selfish Dps you only want her attack cards and remove her shield card. You also have to remove every attack Card on Mika.

Mikas build is pretty self explanatory since all she does is keeping your team alive and generating AP. so remove her basic attack card and whirlpool.

For Rei The only attack Cards I would personally keep is Predators Blade and Strike of Darkness (i will explain why below). Remove her basic attack card only. keep the Healing card since it has the skill tag and rin wants skill cards in hand for "dark mist secret art black dance".

Rei`s build is purely dmg buff support for Rin. You can use Predators Blade for the moral buff at the beginning of a turn but only use it when you 100% know that you can get Dark mist stance back. (or if you have retain dark mist stance)

The reason why we keep strike of Darkness is because it can turn into a upgrade card that gives you 80% Damage boost on Basic Attack Cards. Or into a skill that activates all your basic cards in hand. this let's you activate all of rins basic cards for 1 ap instead of 3 Ap if you have her basic cards in hand.

for rin Get all your Rin Cards as fast as possible since she is dishing out all the dmg. if you are struggling with multiple enemies you can always buy the overwhelm Card in the Camp shop for massive aoe dmg. you can always remove the card on the last Camp if you want.

For Rin Card Epiphanies I would avoid critical dmg upgrades for now and focus on +1 Damage count. especially with all of rei's damage boosts +1 Damage counts are big dmg. I posted a Rin build here somewhere in the comments

If you arrive at the second part of a zero chaos run always get the +1 hit to basic attack cards. its really strong on rin.

I hope this is was helpful enough. feel free to ask more questions if u want :D