>>281430972
Fire was introduced as Justice in the first chapter, speedy.
And she already got wrapped up, what is left is the choice she spoke to Denji about, which is obviously tied to the climax, and most likely to his confrontation with Asaru.

If anything, what the Fire Devil said makes it even more obvious that we're at the endgame since the choice is obviously related to Asa and Yoru to some extent.