Alea jacta est! is an original composition from maimai FiNALE, created by BlackY under a dual credit with his own alias WAiKURO. The title is Latin for "the die has been cast," a phrase famously attributed to Julius Caesar upon crossing the Rubicon River, and the track channels that same decisive, high-stakes energy through aggressive electronic instrumentation at 162 BPM. The song debuted as the maimai national finals piece for the 5th Tenkaichi otogesai tournament, then entered arcades on February 7, 2019 via the PANDORA BOXXX event Phase 3, representing the maimai PiNK era. The artist credit "BlackY fused with WAiKURO" was later explained when BlackY confirmed on Twitter that WAiKURO is his own alternate pseudonym, making this song a genuine solo work framed as a collaboration. All WAiKURO-penned tracks across rhythm games begin with the letter "A," a pattern Alea jacta est! continues. Three of the song's charts carry deliberate design signatures. The MASTER chart, created by HAN∀BI (Kanon Oguni) under the Latin motto "Carpe diem," reuses and recontextualizes pattern motifs from the MASTER and Re:MASTER charts of AMAZING MIGHTY!!!!, another WAiKURO composition, though at a more approachable difficulty that serves as a stepping stone to higher-level play. The Re:MASTER chart, designed by Takanashi-san fused with Phoenix, pushes note density further at level 14+. A long version and a remix by xi (Yusuke Ishiwata) appear on the album ULT!MATE END, and a thematic sequel titled Divide et impera! (Latin for "divide and rule") was later added in maimai DX PRiSM. The song also crossed over into CHUNITHM and オンゲキ, each with unique chart designs by different note designers. The in-game movie was produced by 鑓田 (alpha complex).