Game dumps a boss fight on me rather suddenly and without any particular plot justification. It wrecks me in seconds. Repeat that for multiple attempts for about a week.
Looking it up, the consensus is that this is actually the hardest boss battle in the game considering the point in the game it happens.
I spend a significant amount of time grinding, stocking up on healing items, and making sure everyone has the best equipment I could get them. ...And the boss still wrecks me within seconds. I try again, this time making sure to take a close look at the options for managing party members' AI. This time, it's a very close fight. I burn through almost all my Apple Gels, ALL my Orange Gels, and surprisingly few revive items. Even manage to achieve the Secret Mission objective. Towards the end of the fight, I scan his stats and find he has about 700HP left(out of around 32,000HP). Then the healer gets knocked out just as the mage is casting the finishing attack. I manage to revive the healer less than half a second before the boss dies, saving her from missing out on the experience from the fight.
Tales of Vesperia, Gattuso fight. That was not a fair fight.
Also, why does this game try to access the internet? More than once I've nearly died because my Switch brings up the wifi network search menu in the middle of battle, which locks you out of control until you close the window, which takes several seconds because it insists on searching for networks despite not being able to access any.