>>543435680
>Phase 1
Hit the roomba with your fastest ID before any clashing happens.
Kill all the seaborn you can but don't attack the reapers unless they're awake. Mayors takes damage for every seaborn you kill.
Clash with Mayors to stop her from hitting the reapers herself.
Make sure you win against the big AOE skill she uses once she's below 30 abyssal vitality. You can use Meursault's base EGO the turn before if she's getting close.
>Phase 2
In the combat event, get either the healing boost or anti-stagger one.
Hit the roomba with your fastest ID before any clashing happens.
Win clashes until her shield breaks. Burn in particular shreds her because she loses the "Take -90% damage from statuses" passive in this phase.
She uses another big skill when she's below 30 abyssal vitality so hit her with debuffs the turn before that happens.

The most annoying part is that there's a lot of unavoidable damage that requires you to bring some kind of healing to the fight. You can accidentally wake the reapers up if you're not careful about using AOE skills.