The legendary Chinese military strategist Zhuge Kongming, on his deathbed during the Three Kingdoms period, wishes to be reborn into a more peaceful era. He awakens in modern-day Shibuya, Tokyo, on a lively Halloween night. Disoriented but with his tactical genius intact, he wanders into a nightclub and hears the voice of Eiko Tsukimi, an aspiring singer. Captivated by her talent and believing her music has the power to bring peace to the world, the former general decides to become her strategist.

Having already used his brilliant schemes to help Eiko gain recognition, Kongming sets his sights on a much larger prize: the Music Battle Awards, a high-profile tournament where Japan's three biggest music labels compete for supremacy. Success here would secure Eiko's future. However, he soon discovers that this modern battlefield has its own master strategist. Shin is a mysterious and talented street singer whose music also speaks to Kongming, though in a way that troubles him. She is managed by her brother, Jun Shiba, a descendant of Sima Yi, Kongming's greatest historical rival. Jun harbors a familial grudge and is determined to defeat Kongming, using ruthless and underhanded tactics to advance Shin's career.

The conflict deepens when Kongming begins to experience strange visions of his past life and his beloved lord, Liu Bei. He learns of the Yumi Door, a passage to the afterlife, and is told that the next time he hears Eiko’s music, he will feel an overwhelming urge to step through it and leave the modern world forever. Determined to fulfill his dream of using Eiko's voice to unite people, Kongming accepts this fate, viewing the Music Battle Awards as his final campaign. Eiko, discovering his plan, is devastated and loses confidence, fearing that her singing will cause her friend to disappear.

As Kongming and Jun engage in a battle of wits, reenacting ancient rivalries on a modern stage, the competition becomes more than a quest for fame. The film culminates in spectacular live musical performances, including a major set by the global boy band &TEAM. Ultimately, both strategists are forced to confront the true purpose of their efforts, rediscovering that the joy of music has the power to overcome generational hatred and bring about the very peace Kongming has always sought.