地球 (Chikyū, "Earth") is a maimai original composition by the unit 立秋 (Risshū), a tag team of the doujin rhythm-game composers 竹 (Take) and 田中 (Tanaka), featuring vocalist ちょこ (Choco). The track debuted on August 4, 2023, during the maimai でらっくす FESTiVAL PLUS era, initially locked behind a 300 km mission in the ドラゴンちほー2 (Dragon Area 2) content set. The defining characteristic of 地球 is its extreme BPM volatility, a signature of the 立秋 × ちょこ collaboration that players of the team's earlier maimai original "竹" will recognize immediately. The song opens at a drowsy 79 BPM before a spinning acceleration (marked by EX notes) launches it to 280 BPM. Around the midpoint the track settles into 180 BPM with a 5/4 time signature, then drops back to 79 BPM and surges once more to 280 BPM for its finale. These rhythmic whiplashes give the piece a distinctly episodic, journey-like quality. That journey is grounded in the Dragon Area 2 fantasy narrative, which draws loosely from Norse-mythology-inspired worldbuilding. The accompanying flavor text tells of Ask, a young man from Midgard who, convinced his partner dragon cannot be found in his narrow hometown, sets out for the realm of Asgard. Turned away at the gate for lacking a partner, he overhears ominous rumors of the Dragon King's death at a nearby inn. The song's dramatic tempo swings mirror Ask's arc from restless yearning to desperate resolve. On the charting side, the Expert and Master difficulties each bear their designers' distinctive signatures. The Expert chart (level 12.8, designed by 鳩ホルダー) is notable for its extremely high Break note density, 97 Breaks out of 567 total notes, an outlier for its difficulty tier. The Master chart (level 14.3, designed by じゃこレモン) emphasizes Slide mobility with 147 Slides out of 890 notes, creating patterns that demand precise touchscreen sliding across the DX panel.