It was indeed the idea that Tidus gave him before the last mission. He just hadn't gotten around to it. He'd had to come up with the best way to test it.

"If you feel any adverse effects, don't hesitate to tell me and we'll stop immediately." Senku advised him because he was not trying to hurt his friend.

He removed his own SCA and switched with Tidus, slapping it onto his wrist.

It felt...weird. It definitely felt incredibly strange for some reason, but it wasn't his wrist, or the weight, or anything that might make more sense. It was more like a feeling of unease.

"Once you've got it, I just need you to put your arm on the table near the jar."