Mood: The mood of the video appears to be nostalgic and sentimental, with a hint of playfulness. The theme seems to revolve around school life, friendship, and possibly self-discovery. The overall emotion evoked is warm and uplifting.

Environment: The setting of the video seems to be a school or a educational institution, with the background featuring a school building and chalkboard with mathematical equations. The presence of a group of children in school uniforms also supports this inference.