An overtube system configured to introduce an endoscope into a body, includes a tubular main body formed to be insertable for the endoscope; a balloon attached to an cuter circumferential surface of the main body; a driver configured to inflate and deflate the balloon; and a controller configured to control the driver, wherein the controller is configured to: generate an operation signal for the driver, calculate a relative rotation state between the main body and the endoscope around a longitudinal axis of the endoscope, generate a correction operation signal by correcting the operation signal according to the relative rotation state, and transmit the correction operation signal to the driver to operate the driver.