The Strongest Brave Man of the Black Wizard
Shikkoku Tsukai no Saikyou Yuusha: Nakama Zenin ni Uragirareta node Saikyou no Mamono to Kumimasu / Hero of Darkness / Shikkoku Saikyo / Shikkoku Tsukai no Saikyo Yusha Nakama Zen'in ni Uragira retanode Saikyo no Mamono / Shikkoku Tsukai no Saikyou Yuusha,

Shion, known as the Saint of Darkness, believes his trusted party will help him overcome the Demon Lord. Instead, the young women he relies on betray him, leaving him barely alive and deeply scarred. After losing his powers, Shion gives up on living and wanders through a forest, searching for a way to die. There he encounters a lone monster, which asks him to kill it—even though Shion remains strong despite his loss of power.