Farewell, my angel...

Once upon a time, there were two children named Fukase and Oliver who, one Halloween night, decided to go to an abandoned church known to be haunted. They entered and a young boy, with a hoarse and tired voice, appeared before them, while they searched the surroundings. He claimed to be a priest. Fukase manages to escape, but Oliver, him, panicked noticing the halo floating above the boy's head, proving he was a ghost, passed out. He woke up in a small room lit by the full moon. And so, without really knowing why, he fell head over heels in love with this ghost.