I am talking about the panel on the left in the middle section of the page. The main character (highscooler) and his sensei go to see the main character's sister who has shut herself in a room, inside a pile of empty food boxes. They are going to possibly, get her out of that.
I think the above sentences translate to,
That moment when an outsider wrenches open the shell
Moreover there's a possibility that she has shut herself in the darkness of her soul
Then as per the page, the main character asks if the sensei is kidding because of the first line (above).
What I translated comes to me as pretty weird. Why would sensei say that and I feel like the two sentences are somehow connected but I can't seem to find much connection.