Well .. there is this set up in the very beginning.
MC is presented with the most precious girl in his universe.
There are antagonizing elements running him into the ground and threatening the one girl he holds dear.
So he has a moment of retaliation, runnin his mouth.
MC is coiled in his dark place of terror and only the bright dream of his most fantastic babe ails him.
When you think about it, being this desperate and this helpless,
of course he would turn to the occult, nobody else can help him,
only some ancient demon trapped down below,
threatening his minions to do his bidding, how else would he pass the time?