have to ask anyone know a good way to get sp to lvl up your monster girls? want to max them if you can that is all so is there any way to refight the bosses without going to her room want to fight siren again but can't fighter her in her room without being able to fight her
In order to get SP, you need to let the girls drain your levels.
Equip the indulgence that allows the girls to drain your life, go to my room, and then give all of your faith to them.
Then level up to 36 and do it all again.
The most annoying thing to increase are your character's propensity which unlocks unique scenes per girl.
You don't need to refight the girls to get SP.
If you want to refight girls, save before fighting them, then move to a new save slot, and continue the game after you fought them. Go back to previous saves if you want to refight.