Actually, this probably should go in the "Thinking With Portals" pool. It's actually rather brillant on her part!
"Ropes/chains" made of gaps in space would be physically unbreakable because how are you going to break an empty void hanging in the air? You can't push past them either (you'd be pushing parts of yourself into the portal while the rest remained behind)!
Unfortunately for Yukari this guy's power is basically reality warping as well.
Thanks!We'll leave that big thing to you, Reimu!
We'll try to catch up as soon as possible!OohI thought you'd sneak away somewhere and watch from above......
I should have known you wouldn't be so considerate.