Brave Frontier

Even 5 UBB should never take a whole hour though - at least for me because I'm using Droid4x and I've hotkeyed the guard swipe to be able to guard all in < 2 s. Plus after reading the comments I remembered that you can normal attack to fill OD faster, and after testing a bit I've found that you can probably attack with any unit except Avant (a crit from Avant is guaranteed kill) which brings down the OD fill to about 10ish turns. The only problem I have now is keeping my units alive long enough.

Charla heals and clears status on BB, so she's one of the few ways to pull off 5 UBB. Only other way is Diana and luck with status, hc distribution, and BC on hit.