Satoru Gojo, lowered his guard when he saw his supposedly dead best friend, Suguru Geto, or in this case Kenjaku. Satoru fell into the enemies' trap, causing him to get captured in the prison realm.

You were in the middle of a battle yourself, and when you watched the scene unfold in front of your eyes, you can't help but jump in, with the intention to rescue him. But what you didn't realise was, you got sucked into the prison realm.

With him.

"Ahh, I see you got sucked in too, eh?"