Final Fantasy X-2/Mi'ihen Mystery

The main portion of this mini game happens during Chapters 4 and 5. However, set up for it can start as early as Chapter 1.

During Chapter 3, a hover crashes over a bridge and the machina, which were supposed to be protecting travelers, riot. Speaking with Rin during Chapter 4, he asks Yuna to use the CommSphere network Shinra set up and some extras he has placed to find clues and discover how this could possibly happen. When you do discover something suspicious, give him a call and he will investigate. When enough clues are found, Rin will report that he will be taking over the investigation and thanks Yuna for her help. The results will be unveiled while visiting the Mi'ihen Highroad during Chapter 5.

There are five possible suspects you can pin as the culprit. Rikku, Calli, the Prophet, a small Chocobo Eater, and Rin. You determine which one by which events you view during the game and what events you call Rin in to investigate.

Suspects
To insure all suspects are available to you, make sure to witness these events while traveling the Mi'ihen Highroad between Chapters 1-3.

Which suspect should you go after? That is up to you. Listed below are the benefits of catching each culprit and which events to view to set them up.

Chocobo Eater
Easiest to catch as the culprit. No work really has to be done to blame him. Chocobos will become available on the Mi'ihen Highroad after catching him, however no extra items will be awarded.
 * View the events during the CommSphere Investigation that give him the most points. These include event A and D during Stage 1. B and G during Stage 2.

The Prophet
Possibly the funniest end of episode scene (depending on your humor), done in a "Scooby Doo Mystery" style. Staring YRP as the meddling kids. You don't receive any extra items for blaming the Prophet. Chocobos don't become available on the Highroad and 100% completion toward the perfect ending cannot be achieved.
 * View the events during the CommSphere Investigation that give him the most points. These include event C and I during Stage 1. C, E, F, I, J, L, and M during Stage 2. A, H, and I during Stage 3.

Rikku
If Rikku is the suspect, the end of episode scene can be considered amusing. Chocobos become available on the Highroad and you receive the Ragnarok accessory.
 * During the Cuckoo for Chocobos mission, Don't catch the chocobo until the third stage. This allows you to view a scene in which Rikku jumps from the top of the Ruins and falls on her backside.
 * After completing the Cuckoo for Chocobos mission, return the Mi'ihen Highroad and invite Calli to board the Airship Celsius.
 * View the Stage 1 Event B, and Stage 2 Event K during the Commsphere investigation.

Calli
Chocobos will be available on the Highroad, however you will miss out on the reward from the Cuckoo for Chocobos mission.
 * Do not complete the Cuckoo for Chocobos mission. Decide not to help Calli after visiting the Mi'ihen Highroad during Chapter 2 or fail the mission.
 * Do not invite Calli on board the Airship Celsius.
 * View CommSphere investigation events E and F during Stage 1. Events A and D during Stage 2 and events C and E during Stage 3.

Rin
Hardest suspect to catch. Chocobos will be available to ride for free and you will win Gippal's Sphere.
 * During Chapter 1, make sure to speak to the female Al Bhed technician training machina in an alcove at the southern end (before the Travel Agency) of the Mi'ihen Highroad.
 * Complete the Cuckoo for Chocobos mission during Chapter 2. Return to the Mi'ihen Highroad and enter the Travel Agency to view Rin walking past and exiting the building.
 * Defeat 7 or more machina in the Machina Mayhem mission during Chapter 3. Rin should be in the crowd at the mission end scene if you are successful.
 * Call for Rin during Stage 1 event G when investigating with the CommSpheres.
 * During Stage 3 of the CommSphere investigation, witness clue event G -don't report to Rin yet-, switch to the Newroad CommSphere and witness event D immediately afterward to view the scene and then report.
 * After completing the previous step, view a CommSphere where no events are happening and call Rin five times. He should get irritated and eventually won't come running when you call for him. Take no further steps until Chapter 5.

CommSphere Investigation
There are 8 CommSpheres set up along the Mi'ihen Highroad.
 * Travel Agency, Front
 * Travel Agency, Back
 * Ruins
 * Newroad
 * Hover Crash Site
 * Oldroad Interior
 * Shira's CommSphere
 * Highroad North Entrance

The actual investigation during Chapter 4 is divided into three parts. Rin will inform you when he has moved on to the next stage by telling you that you are getting to the heart of the matter. While viewing events on the CommSpheres, if you want them to count toward the investigation, make sure to call Rin over.

In order to move on to the next stage, you must have viewed so many events toward a suspect. This gets especially tricky when trying to implicate Rin as the culprit. Use the below chart to figure out the number of events to witness per culprit before you can move on.

These tables describe each event that can be viewed during the CommSphere investigation and what is needed to view that event. In each event requisite, if a stage isn't noted, the event that is is during that stage.