Grasshopper is a black humour thriller novel by Japanese author Kōtarō Isaka published in 2004 and later translated to English as Three Assassins. The novel follows a schoolteacher who is drawn into the criminal underworld seeking revenge for the murder of his wife, only to be drawn into protecting a family from a trio of assassins after the target of his revenge is in-turn murdered by someone else. The first novel in Isaka's Hitman trilogy, it was followed by Bullet Train, to which it was marketed as a prequel in English language territories on its translated re-release in 2022, as a tie-in to the Bullet Train film adaptation.