Nanao, nicknamed Lady Bird--the self-proclaimed "unluckiest assassin in the world"--boards a bullet train from Tokyo to Morioka with one simple task: grab a suitcase and get off at the next stop. Unbeknownst to him, the deadly duo Tangerine and Lemon are also after the very same suitcase--and they are not the only dangerous passengers onboard. Satoshi, "the Prince," with the looks of an innocent schoolboy and the mind of a viciously cunning psychopath, is also in the mix and has history with some of the others. Risk fuels him as does a good philosophical debate . . . like, is killing really wrong? Chasing the Prince is another assassin with a score to settle for the time the Prince casually pushed a young boy off of a roof, leaving him comatose.
When the five assassins discover they are all on the same train, they realize their missions are not as unrelated as they first appear.