It is old news, indeed. Something they've actively taunted others with in the past. Chara has never not been trapped, in their entire life. They have practice at it, adapted to it even as they hate it vehemently, because at least that gives them some control.

This is the first time they, as who they are, has been changed against their will in such a way. This is what's bringing the entire affair crashing down.

The other laughs too, and that only increases it, a raw sound. They try to force it to stop, and it keeps going and going until they lean against the window.

"I hate this," they say at the end of it.