Finally played this!
Did two tries, won and lost the final battle! And completed the penultimate battle by phasing the first time and secondly somehow beat it so there weren't any summoned minions.
Now fighting the secret battle! Good music everywhere!
Secret Boss Spoilers for if you look below...
Interesting choice of damage numbers and attacks, such that I never had to Hold, since I always have at least 1 MP, and the last two possible battles are one-on-one duels so Rushing Restore and Rushing Slash were all I needed, if I didn't speed things up with Rushing Burst.
Aww, the secret boss "takes the form you desire most"! And looks like a non-pixelly Harold! Interesting! "I love you!" and all!