Tengen snapped his fingers.
"Exactly! An open domain doesn't have a sturdy shell like a closed domain does.
If it encounters an obstacle while expanding, it can't use a shell to force its way through like a closed domain!"
Yuki Tsukumo continued the explanation.
"Even if a closed domain can't force its way through, that's fine. Once its shell closes, the inside becomes an entirely new space.
And the actual size of the space inside a closed domain has no direct relationship to the size of its shell.
Even if its shell is only as big as a soccer ball, the space inside can still be as large as a soccer field!"
Tengen nodded, clearly agreeing with Yuki Tsukumo.
"A closed domain constructs an innate domain within itself. The actual size of that innate domain has no direct relationship to the size of the domain's shell.
But an open domain constructs its innate domain in the real world, so its size is closely tied to the space it occupies in reality.
An open domain can choose to go around an obstacle, but what if that obstacle forms a closed circle?
Without a shell, the open domain won't be able to break through that obstacle. It will be trapped inside!"
At this point, Tengen finally laid out his plan for Yuki Tsukumo.
"Yuki Tsukumo, as long as you can lure Kenjaku into opening his domain, I can construct a small closed barrier around him.
With my closed barrier in place, Kenjaku won't be able to extend his domain outward.
You might not even need to open your own domain. You could simply defeat him from outside the barrier."
The more Yuki Tsukumo heard, the more excited she became, nodding repeatedly.
But a moment later, she suddenly realized something was wrong.
"Wait!"