Mi'ihen Highroad Mystery

The Mi'ihen Mystery is an optional sidequest in Final Fantasy X-2 and takes place during Chapter Four. Rin asks Yuna, Rikku and Paine to help him investigate two separate incidents that occurred during the game on the Mi'ihen Highroad; a hover crashing on the Oldroad and the sentry Machina going haywire.

Participating in this sidequest is necessary for the player to earn an Episode Complete for the Mi'ihen Highroad.

Story
During the Eternal Calm, the inhabitants of Spira slowly began to accept Machina. On the Mi'ihen Highroad, Rin installed several sentry machina to guard the highroad and protect travellers from fiends. In addition, hovers replaced Chocobos as a more convenient means of travel. The presence of machina and hovers meant that Chocobos are all but gone on the Highroad.

However during the events of Final Fantasy X-2 two separate incidents occurred. After the mission "Cuckoo for Chocobos" in Chapter Two, a hover, travelling from the Travel Agency to the North End, mysteriously falls off the Newroad and crashes on the Oldroad below. This incident closes the Northern section of the Mi'ihen Highroad for the remainder of the chapter.

In Chapter Three another incident occurred. The sentry machina on the Highroad malfunctioned and began to attack travellers instead of protecting them, prompting the Gullwings to battle and destroy the machina while the Al Bhed dismantled them. Following this incident, Rin launches an investigation into the hover crash and the machina malfunction.

During Chapter Three, Shinra installs a CommSphere outside the Travel Agency. In Chapter Four, when the Gullwings connect to the CommSphere, Rin asks the party to help him in his investigation by connecting to the CommSpheres he has placed around the Highroad and alert him if they find or see anything suspicious.

The results of Rin's investigation are revealed when the player visits the Mi'ihen Highroad in Chapter Five.

Suspects
Five suspects can be blamed for causing the incidents on the Mi'ihen Highroad: The Chocobo Eater, Rikku, Calli, Prophet and Rin himself. Blaming the Chocobo Eater, Rikku or Calli will award the player Episode Complete for the area and allows them to ride Chocobos on the Highroad; pinning the blame on Rikku will also award the player the Ragnarok accessory, which reduces the MP Cost of all abilities to zero. If Phophet or Rin is blamed, or if no suspect is blamed, the player receives an Episode Concluded for the area, and Chocobos cannot be ridden on the Highroad, although pinning Rin the blame does reward the Gippal Sphere.