100F boss was virtually impossible to kill in Turn 1 because of 10-hit negate, and at the end, it had 25-hit Guts. If that wasn't enough, there's a 15-turn limit just to piss you off.
I used Pothos to be able to attain a perfect score by having everyone heal back on their own, canceling out whatever little damage the boss did to them as I put defense buffers and maxed enemy attack down. Balsam was the main damage dealer as always; on top of that, she was able to heal back lots of HP thanks to Pothos.