When Rein got to know about the spatial rifts, he became quite interested in that. From the information Rein got after joining the Heavenly Secret Hall, his research about the space increased by a huge margin. This research result even gave Rein a hefty amount of achievement points too, which was a pleasant surprise.
After going through all the results, Rein was very impressed. The Dimensional God temple lived up to its name and had really progressed a lot in understanding the space of this world. So when even this extremely knowledgeable sect was unable to find the demons inside a spatial rift, it attracted Rein's attention.
Rein started to research on this subject and came up with a few hypotheses. But he needed to do more research to be sure if his thoughts were correct or not. So he started his experiments. For the first experiment, Rein tried to mark a demon to see if he could track it even after it had entered the spatial rift.