Yuri's final ending is not yet known, the show's third season has not yet aired. In the season 2 finale, Yuri wanted to replace Nano as the new controller of life and death.

And she did so, choosing to team up with Jun against Nano. Originally, Yuri passed away, but in the moment of her death, because she drank Nano's blood, she ended up being resurrected and had powers similar to Nano's.

Only, Yuri thought she had what it took to replace Nano, so when she thought Nano was really dead, she excitedly left with Jun. Except she didn't see the school building, where Nano was still standing on the roof watching her if she turned around.

Nano, being the controller of life and death, couldn't have died so easily. What's more, Nano was not a human being herself, and was mainly responsible for punishing the wicked in the human world, amplifying the desires of the wicked, and in the end, letting the wicked be devoured by their desires and eat their own evil.

While Yuri subjectively believes that Nano is dead and thinks that she can replace Nano, she forgets who saved her and who treated her as a true friend, and Yuri is, in the end, consumed by the desires of her heart.