[ The circus was a heavily traumatizing event for both of them. It still crushes Yuzu that she’s probably the reason why the circus would haunt Mabel. ]

I... after I got myself away from you I... couldn’t keep control of myself for much longer. While I was out of control... there was another Shade who was about to eat a soul and I... stole it from him.

[ She can probably piece together what Yuzu then did with said-soul in her wrath-induced state of mind. ]