If you want me to create a spoiler, then fine.

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With the information provided, this is probably a Jeckel and Hyde situation. One of the teachers, probably actually a female, had probably previously lost their husband to a 'younger model'. It would explain why they target young women with rings, as they associate them with the person who stole their lover.

The murder location is probably the Mirror World, which implies that unlike the Metaverse people can by drawn in by the controller of an area.
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Of course, that is all speculation based on the current facts available.