This sound is recognized online as the phone notification from Alice in Borderland, the Japanese live-action survival thriller series released on Netflix in 2020 and based on the manga by Haro Aso. Short clips of the alert spread through fan edits, anime-adjacent compilations and suspense memes because the tone immediately suggests danger, rules or a message that changes everything. It remains popular because it is simple, very short and easy to sync with captions, chat bubbles and reveal cuts.