Dream Magic Heroes

Thanks for playing, and for the feedback!

You should still be able to progress even without the gacha, in fact the main story is balanced around never touching the gacha (other than that one scripted story segment about it), to account for terrible luck. But if you really wanted to, you could always replay the previous stages/bosses to get more pulls? Even if you don't get new characters, you'll still get equipment which can help quite a bit.

As for 5-5, I suppose you're running out of Sanity? (Boss can't endlessly stun everyone, but running out of Sanity on everyone might) If so, the trick would be ensuring that doesn't happen in the first place. If you just want a hint, try observing the boss's attack patterns and the statuses they inflict; they're pretty much the same attacks/statuses as the previous fights, so a mostly similar strategy would work. The timing of when you use support abilities will be important here.

If you just want the solution...

During the first phase, the boss cycles between using 5 abilities based on the current turn count. So it always starts with  C???????? ?? S???? (Cacophony of Souls), followed by I???????? D??? (Impending Doom),  S???? ?? D???? (Seeds of Doubt), W????? ?? R?????? (Weight of Regrets), and finally, D????????? W??? (Discordant Wail) in that order before restarting the cycle.

You'll need to deal with Seed of Doubt before it spirals out of control, so use your support abilities (Yume's Dreamland, Midori's Restore, and Ayumu's Haste) after it's applied. Impending Doom does get applied the previous turn, but since it takes 4 turns to take effect, you can hold off dealing with it until after Seed of Doubt is applied and then deal with both at the same time. Other than that, it might be a good idea to hold off using support abilities until you need them, both to conserve mana for when you really need it, and to avoid triggering Discord more than necessary. If you foresee you might not have the mana you need in the turns to come, it might also be a good idea to spend a turn or so guarding to regain mana faster.

You can also guard against C???????? ?? S???? to prevent the extra Sanity loss, though that ain't strictly necessary. Also worth noting is that since the cycling of boss abilities is based on turn count, you can potentially 'skip' abilities you don't want to deal with via sleep/paralyze (though the latter might not be as reliable).

Once the second phase starts, you can (and probably should) kill the additional enemies that spawn to regain Sanity.