Daijoubu is an everyday Japanese expression meaning all right, okay or I'm fine, and it appears constantly in anime dialogue during injury, worry or recovery scenes. Short reassurance lines like this spread through anime soundboards and edit communities because they are easy to reuse out of context, similar to how tuturu became a standalone reaction sound. Its popularity comes less from one specific scene and more from the universal joke of calmly claiming to be fine when the situation clearly says otherwise.