Hey, just checked your build.
1)You are still lvl 35. You can do one more Debt quest and get lvl 40 cap. You can sell materials and consumables, as well as excessive gear, to get the gold.
2)Your Tamamo doesn't have any Trinket. I recommend getting "Arcane Funnel" trinket, similar to your MC's, from Koyanskaya for additional Mana regen. With this one, she will heal and give MP to allies more often. Try to get one with INT for her. You can reforge trinkets as well.
3)Your MC doesn't have ANY set bonuses. You can get something simple like Knight Set + Mage Set for additional life and MP regen. Or you can get 2-piece Trinity, you already have new Wildwoods zone unlocked, and 2-piece Nun sets. Also you can reforge his Syringe Gun for additional mATK.*
4)Your Taihou doesn't have any trinkets. I would recommend "Double Edged Dagger" from Koyanskaya, but if she can't survive without the shields, then you can farm Outskirts with the highest Corruption stone for "High-Roller's Dice", which is just a damage increase on average.
Additionally, Taihou REALLY wants "Navy set", because that set bonus will also duplicate her planes buff, and "Quadruple 380mm" for splash damage.
5)Now THE MOST IMPORTANT PART! :)
Your party doesn't have a "proper" Tank. Jeanne is conditional and is not really reliable for that role.
I recommend replacing her with Artoria or Mudrock. You would notice right away that their base high Threat is already doing its work. You can equip them with the same gear as your Jeanne, or replace it with "Sarkaz" or "PubSec" sets. For trinket, I recommend "Pocket Shield", "Cursed Doll", or "Broken Stopwatch".
Additionally, you can tinker with your Talent tree, as it works for your entire team.
Also, most your your gear is +0, you can enchant your gear at least to +3, as each +1 gives 10% increased stats.*
And for that fight specifically, Kafka's main problem is her Charm debuff that forces your units to attack their allies, so I would recommend using "Scroll of Purification" when you receive that debuff.