The gem produced by the contract of the girl selected by Cupid is the source of magic, the proof of the magic girl and the container of the magic girl's own soul. After Cupid was extracted, the soul and body of the magical girl were separated, and the magical girl became a "zombie". At this time, the soul gem is their deity. The body is remotely controlled by the Soul Gem (SG for short), with a radius of about 100 meters. When the soul gem is broken, the magic girl dies. The use of magic, the consumption of magic in battle, or the despair of the magic girl herself will make the mental nucleus turbid, and it is necessary to suck the pollution with lamentation regularly. If the filth is not sucked away in time (until the soul gem turns black completely), the magic girl will become a witch, and the soul gem will become a seed of sorrow (GS for short).