A god broke taboo.
"Heretic!" "Disgrace!" "Foul!" "Betrayer!"
All other gods wants the god who broke the taboo dead or sealed into somewhere even gods hate.
The white void.
But of course there is no one who will take lying down and doing nothing.
But gods are known to like entertainment.
So a group of gods who don't care of taboo actions or items proposed a bet.
A bet that the sinner god who broke the taboo will have to survive against hundreds of gods.
Of course god cant do anything but watch only summoned creatures can fight.
And so god summons someone who is tasked to defend god.
Joh-... Sun Tzu!
[dunno why it says sci-fi romance...]