Shiome's objective isn't actually to prevent the rifts from closing, that's why I only said it would screw with her plan but never said how. The key idea made me think of this: What if the way to close a rift is to prevent it with an opposite form of the rift? As a comparison, sound waves can be cancelled by mixing them with a frequency that conflicts with the sound wave, and this is how noise cancelling headphones work - they mix in the opposite of the background noise. This is also why noise cancelling headphones only cancel noise when turned on. So, to close a rift, one would generate some kind of anti-rift and have to push the anti-rift into the rift, upon which both the rift and anti-rift would cease to exist?