From what I saw in the video the seal doesn't actually go on the target, it just draws them in if they're in contact with it. That's what confused me. One could argue she is below the inscription, not above, if it is on her, and thus couldn't be sealed. If you really wanted to just try and be a troll anyway.
I just don't really get this whole argument. If I was holding hands with someone, even if I did trust them, and I started getting sucked vacuum cleaner style into their hand I would react in someway to it. I don't think you need to meta-game to understand that it is a bad situation.
Unless she is being sucked in so fast she cannot react, which as I mentioned I don't think would be realistic, then she could at least attempt to do something. She tried to Landmine fist his arm off right? And that was called metagaming I believe. I don't know, that seems like an appropriate reaction.
He already tricked her into releasing her brothers Edo Tensei so he is "dead". I say let her blow her and his arm off to stop the seal and then continue with the rp from there.
All Yujo had to do to give her no chance to fight back was instead of trying to suck her up put some seal on her that would have knocked her out in this exact same situation, and we'd have none of this arguing about a response. He shouldn't have given her any wiggle room, it's not as efficient as it could have been.
It just seems like Yujo went into this expecting to take them both out without a fight and isn't willing to accept any outcome besides that.
If you infiltrate enemy territory by yourself and plan to take out two key people (been playing a lot of Metal Gear V) then your plan can't have any holes in it. Everything on you, behind enemy lines, is as much pressure as a plan can be under and if there are any holes in it that pressure is going to force something out.
Yes this whole situation is basically a fart.