After Failing the College Entrance Examination, I Had No Choice but to Raise Ghosts

[Urban + Supernatural + System + Suspense + Thriller + Development + Multiple Female Protagonists] Unexpectedly failed the college entrance examination. Su Mo who doesn't want to repeat the course. He had no choice but to inherit the family business and raise ghosts. Just when he was worried about how to make a contract with the devil. But suddenly it was bound to the most powerful ghost-raising system. So—— You made a contract with a school beauty ghost, and was rewarded with the "Five Thunder Methods". Your contracted ghost breaks through the high-level fierce ghost and is rewarded with Yuanyang Spirit Pill. Your contracted ghost kills the headless ghost and is rewarded with 1000 mana points. … If you raise ghosts, you will become stronger. The stronger the ghosts are, the stronger I will be!