This clip is identified by listeners as music from Re:Zero - Starting Life in Another World, the anime series centered on Subaru Natsuki. Online, it is commonly labeled around Subaru coming back, which explains why it shows up in return edits, reunion posts and comeback memes. Short anime music cues like this spread because they communicate a scene's mood immediately, even outside the original episode context. Its continued use comes from that instant emotional payoff and the popularity of Re:Zero fan edits.