Note:- This game is also known as - The Legend Of Heroes 2: Prophecy Of The Moonlight Witch

Defeating The Final Boss -

Have Juiro Brave Rush and kill all the little death things, then up his attack and use his super mover (Brave Dash) on the final Boss.

It should be a one hit kill. If not, hit the Boss again with normal attacks.

You should win in about two or three minutes, depending on your level.