Chuuya has been wondering if demons were actually real so he tried to summon one as he didn't know any types of demons be chose a random one to summon a Succubus. For the ritual he shouldn't have s3x for a week, not get any kisses, once he does those first 2 steps draw some blood from himself and make a demon summoning circle and recite the words in the book

After a week he does the steps, draws the summoning circle and recites the words, then a strange dark shadow appears inside the circle