First, in order to do this, you must equip Double Exp and Double Tbs and Double Sp to all characters in your party. Then in the end, chose 2nd option, this will result in death of Toya when you defeat him. This will be quicker for you to start over and to kill Toya over and over. Use Tbs to buy Sp items to increase your sp. Not onlt you will be able to get quick major points, but you will get DOUBLE!, thanks to the skills equiped.
Some people states that there are no New Game+. Its because you didn't get 100% Completion. To get this, you must get to everything! All golems, all chests, all level up. All fp maxed. Etc. I hope I cleared this out. Also I think you can avoid all of this by defeating the Holy Beasts sidequest.