Analysis:Terabyte Disk

It's recommended to read this page after reading "Does History Change?".

Where the Terabyte Disk was Read
There is a computer in SPHIA. But you never see the actual "body" of the computer. The monitor is just connected to a LAN cable. The computer has a keyboard and mouse. But we never see a media device that can read the terabyte disk.

In other words, you need to use another computer to read the terabyte disk.

In SPHIA, the only place like that is the small room in the basement. Yuni and Utsumi probably read it there.

Therefore, they must have eventually met Enomoto. The proof of that is when Enomoto was killed, Yuni and Utsumi behave differently than Kokoro. They never asked "who is this person?" or anything similar.

When the Terabyte Disk was Read
Next, when did they read the disk? Utsumi said she read it after Kokoro's consciousness looked in the mirror, but before Satoru's consciousness woke up (ie. while α was in control of Satoru's body on the 1st day).

There is another time in the story where they went to read the disk. On the 2nd day in Kokoro's route, Kokoro looked for Yuni everywhere after breakfast but couldn't find him.

Yuni would have been in the basement with the terabyte disk. After that, Satoru's consciousness visits Yuni's room where Yuni and Utsumi were having a long talk. It was probably related to the terabyte disk.

Overview of the Contents of the Terabyte Disk
According to Utsumi, "many gigabytes of text and prophecies" were on the terabyte disk. So what was written on the disk?

Let's summarize what the story told us.
 * Regarding Satoru: it has his name, says he suffers from DID and mentions his relationship with Mayuzumi.
 * Regarding Yuni: the disk says the reason Yuni is in SPHIA is because "Kusuda Yuni exists to exist".

Other than that, the contents were extremely persuasive which caused Utsumi to believe it. Only Yuni and Utsumi know the contents in detail...

The Purpose of the Terabyte Disk
Not everything that's written on the disk is necessarily true. The disk says Satoru has DID, but that is actually incorrect.

Whatever the truth is, the terabyte disk probably said that the avalanche killed Kokoro and the others. In order to preserve "the history for the player", false information was necessary. This lines up with the goal of the Yukidoh Plan.

How much was written?
In the timeline, it says:
 * The disk indeed included various information —— "Information only the reader would know" or "All the information the reader wants to know"

It seems the disk contained information about the Yukidoh Plan and all the events that lead to its successful completion.

According to the timeline, the data on the disk is encrypted, but since Utusmi was able to read it there must have been an unencrpyted section. It's possible the unencrypted section contains false information to mislead the characters, while the encrypted portion contains the full details only known to Sunglasses.

Author of the Terabyte Disk
The main purpose of the terabyte disk is to aid the Yukidoh Plan. That means the person who made the disk was Sunglasses and Yuni.

In the story, the terabyte also goes round and round between 2011 and 2012. The terabyte disk continues to loop infinitely, long after the history that originally produced it.

There's no way to know what happened in the original world where the terabyte disk was first made. It's likely that information is added to the disk little by little each time it cycles.

The Yukidoh Plan in the "original world" seems to be different. Specifically, there's a high possibility the terabyte disk made as a result of failure. The fact the terabyte disk from this world is circulating means that they were at least successful in transferring Yuni from 2012 to 2011.

Summary

 * The terabyte disk was created by Sunglasses and Yuni.
 * The disk contains information about the Yukidoh Plan and the events of 2011 and 2012. The disk contains encrypted and unecrypted information, and some of the information on the unecrypted portion is false.
 * It's likely the disk was created since the Plan failed in the original world. More information was added to it as it cycled.
 * The disk was probably read by Utsumi and Yuni in the little room in the basement. That means they likely met Enomoto on the 1st and 2nd day.