Thread:Silver-Haired Seireitou/@comment-4869113-20141002012750/@comment-2089817-20141002013811

Sei used Uchuu to basically create a boundary between the spacetimes, so this dimension is cut off from the normal space time, meaning the only way to destroy it would be to defeat the clone utilizing the Uchuu or somehow disrupt its concentration before you'd be able to use spacetime techniques to escape, but keep in mind that that particular clone is within the Kaguyahime together with the real Sei and Ryun.