This is essentially a slight tweak to my initial Enna Kros run. I was rewatching my run and I realized I could have reduced the turn count earlier simply by popping summon earlier.
It works on this stage because the boss doesn't have any treshhold attacks to skip anyway and Enna absolutely pwns the boss in 3 actions.
Check out the initial run here, complete with video commentary on the fight
Setup
Enna Kros with 5/5 UW, Cid Raines LDCA. If you don't have Cid Raines, try Prishe LDCA and use and Ifrit summon instead
Unequip Buff Speed Up passive: This increases the likelihood that Enna will start last in turn order.
Iroha with 5/5 UW, but her UW isn't needed at all, Cait Sith LDCA. If you don't have Cait Sith, try General Leo LDCA. If you don't have Iroha, use Ursula and don't use the Raines base call in the fight.
Lunafreya with 5/5 UW, WoL LDCA. This call is mainly to set up so that she gets delayed by Shockwave Blade++ without taking damage.