@regalia001 | Nah, pretty sure he's already dead in the Demon Leo's world
"How did he die?" is probably due to an accident/incident that happened either because she rejected him or because it was too late to make a confession. Suicide is also a probability.
[For clarification mods/admins, this is just heavy speculation that resulted in a lot of hypotheses (plural), I don't have the ability to see into the future]
Merry late Christmas for everyone who's reading this