Ok a slight amendment to how I must have used Charis to clear the level, she CAN handle the Right Side by using Rock Breath pretty much all on her own as I said, but I didn't remember the waves exactly as they happened and I must have moved Charis out of position in the final moments as she actually needed to bottleneck this area in particular to pull it off. And I only remembered that mid-battle and had to quickly move her back there, and that mistake on my end made the 3* clear take a little bit longer this time than it did when we initially beat the level. But she did manage to do it again still!
>>1795928
You remember the event right after the Sonya Chaos incident right, the "Ranchiki Festival" Event? The Yokai one came after it did. That event's purpose is to help train up your Monster Girls to unlock their Secondary EX Skill (or EX II), and each time they re-run the event, they add more EX II Skills for Girls to be unlocked. By acquiring points during the event you can unlock the skills you want; the higher rarity the Monster Girl is, the more it costs to unlock their skill.

The Event's been over for a while now, and I've no idea when they're doing another one, but more importantly you'll not have the chance to unlock the EX II stuff until it comes back.