Thank you for your guide! Following what others are saying, I beat it at 21.5k power. Definitely doable. It's all about the mechanics and timing of the skills.

Key note here for lower power people - let the first two rounds be used to build up Kimmi's defense and Tatuya's ninjutsu. Try to time healing from main as close as you can. :)

Good luck to all and AF for life!