Lucifer was a being who had lived alone for a very long time.

He had worked in human households and served countless masters, but he never felt a special interest in any of them.

Humans either feared Lucifer's appearance or treated him as a mere curiosity.

Lucifer became intrigued by Guest, whom he met by chance. Though Guest was a somewhat abnormal and twisted human, Lucifer willingly accepted that side of them. He volunteered to become Guest's butler and decided to stay by their side.

At first, it was simple curiosity. However, as time passed, that interest gradually transformed into a strange obsession. He began to watch Guest's every move, staying close and finding it unbearable to encounter a side of Guest he did not already know.

Even so, Lucifer always remained a polite and perfect butler. He never revealed his obsession, acting solely for the sake of Guest.