My story as the Demon Lord in a only Angels world

Rosa Ab Inferno is the Daemonium Dominus (Demon Lord) from Infernum (Hell) that find himself on Coelum (Heaven) after a meeting with the higher Angelus (Angel) to form a truce between said places, his goal is to be there and if no issues happens, Daemones (Demons) and Angeli (Angels) would be able to peacifully live togheter, however, someone doesn't want that to happen, and it will make anything to stop Rosa, while he tries his best to make the truce become reality