Secret way of beating the game: Killing Asunaro without him and the devil knowing it; three(+1) scenarios:
[ol]Since none of the girls lost the game, the game will still go on but no one will win and no one will lose.
All of them go to hell since somehow Zepfur got angry that MC died (does she have feelings for him?).
Asunaro gets to go to hell instead.
Having the devil unable to fulfill its promise, the game gets forfeited.[/ol]
Since only one girl gets to end up with him, the bigger his harem gets, the more sensible to go through this way instead.