Levi's Unknown Cleaning...

is an extra chapter included in the second volume of the Attack on Titan: No Regrets manga, written by Gun Snark and illustrated by Hikaru Suruga.

Summary
Late at night, Isabel rests nervously in her bed, recalling a time from earlier that night when Furlan told her of a scythe-wielding monster that comes out on humid nights like tonight. Furlan is amused at how easily he spooked Isabel.

In her bed, Isabel stares nervously at a stain on the ceiling above her, seeing the face of a ghoulish monster. On the floor above, Levi notices one of the barrels is leaking its liquid onto the floor. As he grabs the barrel, the floor beneath him gives way, sending him falling into Isabel's room. Isabel leaps out of bed, Vertical Maneuvering Equipment at the ready. As Levi asks her what is going on, she panics, thinking that he is the monster as Furlan runs into the room. Shortly afterward, Isabel is cleaning the mess while Furlan looks up at the hole in the roof and Levi sneers at his dirtied clothes.