Tale Of The Gods

A world where 3 Gods rules, deities relying on humans' faith to live or cease to exist, and where coexistence with what we call mythical creatures is possible. A world where we might think is quite different from the world that we know but not at all, it is the same world our current humanity exists in.
Levin, the death goddess, went on a quest to find the answer to her Divine Father's enigma in which she met a skeptical human, Sa Hansol, who turns out to hate the Gods and blames them for his miserable life.

When an arrogant, conceited, Death Goddess, who has deep grudge against humans, and a distant, misfortunate, Human, who has a profound hatred against Gods, meet, would the vague riddle be answered?

"What death does not know, death will aim;
What death does not have, death will gain;
In the search Death shall obtain
Both a treasure and a pain
Once solved and figured out it will show,
The most powerful one of all"