第４のユニット ＭＥＲＲＹ ＧＯ ＲＯＵＮＤ

Koshinaka's research of the data bank on board the Diabolique, a stealth aircraft carrier of the United Nations, is aimed at increasing the life adjustment factor of bionic soldiers. However, members of the Einheit assault the laboratory, and the bionic soldier Blon-Win must decipher the clues left in order to proceed with the research and confront a mysterious person named Rua Rip Salisbury in the Original Matrix.

"Merry Go Round" is the sixth installment of "The 4th Unit series" and a sequel to "D-Again", being the second chapter of the Einheit story arc introduced in the previous game.