To get the second ending you must defeat Zophar and then save the gave afterwards as the “Epilogue” entry. Basically you need to regroup your party members and go through some scattered dungeons around the world to obtain two dragon jewels to enter the Star Dragon Tower. The star Dragon tower is found in the starlight forest. Once you fight your way to the seventh floor you must face the Star Dragon boss with just Hiro.
The battle is pretty simple. I found myself just using the triple strike move over an dover again on the dragon, pausing once to replenish my life with a healing nut. After this you get to see the final ending of the game along with some humorous outtakes after the credits.