Adult PC Game: Otaku's Fantasy 2 Ver.1.03 by Dieselmine Archive

In face of the evil monster girls that suddenly appeared,
humanity stood no chance, life force mere sustenance
to be devoured and their lives snuffed from this mortal plane.

When all hope was thought lost,
the protagonist falls from a cliff when wandering a mountain,
in search of a haven free from the assault of monster girls...

Oops... is all hope lost after all?

No! Upon awakening, he finds an unfamiliar sword in his hand.
"Use the LifeSword, and save your world from devastation."
He hears a voice resonate from somewhere...
Can such a weak young man like himself really save the world...?
Half in doubt, the protagonist takes the LifeSword and challenges
a monster in battle but... his expectations are totally betrayed.