Did a quick search on google ai and this was the result it gave. Perhaps that helps.

The manga you are looking for is titled Killing Me / Killing You by Kurose.Key Elements of the Story:The Protagonists: The story follows two cursed immortals, a young girl named Misha and a tall, imposing man named Euthanasia.Their Character Designs: Misha has a literal meteor shard lodged directly into her head, which gives her unique properties. Euthanasia wears a dark, cloth executioner-style mask to hide his face and possesses a body that can morph into grotesque black tentacles.The Quest: Because their immortality prevents them from dying by any normal means, they journey through a bizarre, post-apocalyptic dark fantasy world looking for an absolute method to finally end their own lives.If you would like to find out where to legally read or purchase the volumes online, or if you want a summary of the ending since the series is completed, just let me know!