"only my railgun" is the opening theme of the anime series A Certain Scientific Railgun (とある科学の超電磁砲), performed by the electronic J-pop unit fripSide with lead vocals by Yoshino Nanjo. Composed and arranged by Satoshi Yaniguma, who co-wrote the lyrics with yuki-ka, the track was released in 2009 as fripSide's major-label debut single and quickly became one of the most widely recognized anime theme songs of its era. The song was added to maimai FiNALE on December 13, 2018, the arcade version's launch day, placing it among a small number of third-party licensed tracks available from day one. Its Re:Master chart was also playable immediately, an uncommon milestone for a newly imported licensed song. The maimai edit runs approximately 1:40, shorter than the full single's 2:22. (The CHUNITHM series uses a separate cover recording, while maimai and オンゲキ both feature the original fripSide version.) Licensing has made the song's regional availability uneven throughout its maimai lifespan. It was omitted from the Asian release of maimai FiNALE, restored in non-Japanese versions of maimai でらっくす, then removed again from Chinese cabinets starting with 舞萌DX 2021 and from Asian-region cabinets with the maimai DX BUDDiES PLUS update in September 2024. As a result, the song is no longer accessible on current Asian and Chinese arcade releases. The chart set spans five difficulties (Basic through Re:Master), with credited designers on the upper three charts: 華火職人 (Kanon Oguni) on Expert, 緑風 犬三郎 (Happy) on Master, and LabiLabi on Re:Master. The song's level assignments have been revised several times across version updates, the Expert chart rose from 9 to 10, the Master from 10+ to 11, and the Re:Master climbed from 11+ in FiNALE to 12+ in BUDDiES+, reflecting ongoing recalibration of the chart's difficulty.