Yukinojo

This is my hypothesis, the place that Momo and Tenchi were in was a storm, unfixed point or distorted point in time and space. The reason why Tenchi was thrown everywhere because of the unstable distortion, the only constant was Momo and her timeline. The DOB and Toshika acted as a constant that was strong enough to create a place for Tenchi and Momo to meet and get back.

The Keys channel energy and possibly make temporary time and space distortion stable for a time. Momo was probably not strong enough like Tenchi and need the DOB and Toshika to give her something to lock on to. Tenchi came to her in a point where he first met in her timeline, the oldest version of her in the beginning of the blipping and last time they met, before the youngest version in the last episode.

From his comment, one does wonder if all her barriers and mini-guardians before were not her manifesting Jurai’s power, or perhaps just a low-level utilization of it. However, she is undeniably channelling Jurai’s might with purpose, likely using her tiara in doing so.

Powers Thread explains a bit. I think the Keys are tools to help access and control powers. But they might have programs or functions imbedded in them to help them focus better. It’s easier to use power when there is a preset function of a mini guardian or shield that can focus energy.