Well, in 10 chapters, his power will most likely be at 1 trillion.
I still prefer that to long, boring arcs where this ecchi harem manga becomes a fighting one.
And I really don't see a reason why this shouldn't have a true harem ending... secret societies, ninjas, monsters and ghosts... so why not polygamy. Those girls don't seem to mind sharing him, it seems.
And he clearly has the stamina to "provide" for everyone ( ͡° ͜ʖ ͡°)