Demon Slayer: Clear Sunlight, Gentle Breeze

An orphaned boy is taken in by a teahouse owner and starts working at his shop. He thinks his happy life will last, but a demon shatters his hopes, turning them to despair. Unable to accept what has happened, he fights back with all his might, but he is no match for the demon, having no strength to fight at all.

Just then, he meets [Flame Hashira] Kyojuro Rengoku. Kyojuro saves him, and the boy successfully becomes his little shadow.

P.S. I'm no good at writing blurbs. If you're interested, come debate it in the story.