So, I skimmed through the raws and I think the culprit is the princess.
After MC and ML get married, MC dreams (?) about what happened after she died, so she saw ML cry over her dead body and he kinda went batsh*t crazy, picked her body and went into a killing spree all bloodied up. After that he was sentenced to dead, so yeah, his ending was being beheaded and his eyes were basically soulless since MC's death.









omg didn't expect this one to get a manhwa, I can't wait for that part to come!!