封焔の135秒 (135 Seconds of Sealed Flame) is an original composition written for maimai でらっくす PLUS by the enigmatic artist 大国奏音 (Kanon Oguni). Added on August 7, 2020, as part of the Heavenly Realm Area 2 (天界ちほー2) unlockable content, the track runs exactly 135 seconds (2 minutes 15 seconds) at a driving BPM of 200, a duration reflected directly in its title. The MASTER chart mirrors this numerical motif with precisely 135 Break notes, a deliberate easter egg that ties the song's identity to its name. The identity of 大国奏音 was initially a puzzle for the community. The name deliberately mirrors 小国奏音, which appears in the credits of other SEGA rhythm-game tracks such as "Believe the Rainbow" (maimai) and the ONGEKI ending sequence. ONGEKI bright MEMORY's END CHAPTER eventually confirmed the reading "Kanon Oguni" for 大国奏音, but the full picture came together on maimai's official 10th anniversary website, where the artist was credited as 大国奏音(華火職人). This confirmed that 大国奏音 is the same person as 華火職人 (Hanabi Shokunin, "Fireworks Craftsman"), a creator previously known for designing charts under the 譜面ボーイズ (chart boys) circle rather than composing music. 封焔の135秒 thus marked the first original maimai song ever written by a chart-boys creator, a milestone in the series' crossover between chart design and music production. The MASTER chart, designed by 7.3GHz vs Phoenix, gained attention for its signature cross-directional slide patterns: right-to-left slides paired with left-to-right slides that demand simultaneous use of both the touch screen and physical buttons, making coordination the key challenge. The EXPERT chart was handled by はっぴー (Happy). Beyond its in-game presence, 封焔の135秒 was selected as one of the online preliminary songs for the KING of Performai 2020 tournament, during which it was temporarily playable without unlock restrictions from October 1–28, 2020. The song transitioned to general unlock availability starting with the Splash PLUS version in March 2021.