エスオーエス (SOS) is the designated theme song of maimai でらっくす BUDDiES PLUS, the second major content update to the BUDDiES edition of maimai DX. The track was produced by カロンズベカラズ (CaronzBekaluz), a unit formed specifically for this commission, uniting vocalist SymaG (島爺) with composer, lyricist, and arranger Nanahoshi Kangengakudan (ナナホシ管弦楽団). While SymaG had previously appeared in the maimai series as the vocalist for Secret Sleuth, this release marks Nanahoshi Kangengakudan's first original contribution to the game. The song is a high-energy rock piece driven by a brisk 196 BPM tempo, with lyrics in Japanese that weave imagery of desperation, detachment, and a search for freedom, matching the SOS distress signal of the title. Its music video, created by にへ with illustrations by Masako Wada and 高出力, features the original maimai characters ALAALA, BOUBOU, and RAIZAN appearing as players, embedding the track directly into the game's cast-driven narrative. The accompanying in-game flavor text sets up a comedic scene: BOUBOU, a cat-like alien, and a pair of thugs pick a fight with the wrong opponent, a grinning long-haired girl, leading to a fighting-game showdown that mirrors the track's competitive energy.