This is me speaking to myself, in a corner of this dying world.
Our universe is destined to perish momentarily.
And the culprit … there’s no mistake, it’s “them”.

It all started with a message.

A message of unknown origin, which is contained by this disc. I did not know where or whom it was from.

Of course I couldn’t know, because it was a message from another universe.
A universe above ours - a higher-layer universe.

What the message said was truly astounding.

There are other universes residing in a layer above ours.
There are also other probability universes in the same layer as our own (!).
And this disc could let us see the other universes in the same layer as ours.

But what it showed us -
Were worlds being contaminated, eroded, and destroyed by “them”.

I’m sure it was “them” who caused
the neighbouring universes to become like this.

And when I realised this, “they” are already here in our universe.

I wasn’t able to play around with this message.
That is to say, our sound will not reach anybody else.
The only thing we can do, is to watch over while sending this message to lower-layer universes.

Please, let this message reach universes where “they” don’t exist,

before “they” - the “Hifuu Club”, destroy all the universes.

…… but actually, we know.

When this message reaches you… it would already be too late.

I’m sure something like this will also happen to the next universe.

Our neighbouring universes are already contaminated.

Because well, this message itself is aimed at the “Hifuu Club”, isn’t it?

If that’s the case, we are already contaminated. We are no longer able to think of a universe without the “Hifuu Club”.

Those who made this message in the first place, who knows what they were thinking?

Ah, then let’s just

Spread it!

Spread it far and wide! Let the Hifuu Club reach many, many, many, many more universes!

In the source code of the secret webpage found through the QR code in the album booklet, there is a hint to reach another secret webpage which contains the uncorrupted Divine Message audio (i.e. Activity-log-21-12-12). This also explains why the Hifuu Club has three people, but the project is called Tetra, the Greek prefix for “four”. (tl;dr: you are the fourth person).

According to the credits on BK, the whole text is read by Merry = Meramipop.

By the way, the backing music sounds very similar to Gymnopédies (shudders in The Gymnopédies Never End…).

• U0000-0000000-000000000: Hifuu Club transmitted a message to lower universes.
• U0001-9134845-120368896: the message was scrambled before being received by this universe. People in this universe misintepreted the message segments, and thought the higher-layer universe was going to save them (due to hearing words like あなたの助けに (be your help), and only hearing the first half of 掬い取って (“scoop up”), which sounds the same as 救い (“salvation”)). They even constructed a System to spread Project Tetra, as a way to repay their saviour’s kindness. The System is also able to scan many universes within the same depth layer.
• U7730-■■■■■■■-■■■■■■■■■: People in one of the universes in this depth wrote the burnt letter mentioned above. After observing their neighbouring universes die in many different ways through the System, they thought the Hifuu Club was a contamination that destroyed universes. They wrote the letter to warn lower universes, but knew this was futile and decided to spread this contamination further downwards anyway.
• U7731: I think this is the layer our universe, as the System can only search for the other universes in the same layer as it is currently on i.e. ours. The other album tracks are from our neighbouring universes. Also, track 10 is possibly the most close-to-original rearrangement from RD, maybe this is hinting that track 10’s universe is the one where the real Touhou Project, and thus we, exist.

This system is designed for the Most Exalted Project.
The purpose of this complex system is to observe possible universes, and to spread the Divine Message.

When this System is running, it is able to collect the Possibility Depth Layer and Possibility Coordinates of the Universe that the System is currently in.
Afterwards, it is able to collect the states of neighbouring Possibility Universes on the same Possibility Depth Layer, and to output information on those universes.

≪The Meaning of the Existence of this System≫

We of the universe U0001-9134845-120368896, on the date 20■■-12-12, have received a message from a higher-layer universe.
The message was fragmented, but it clearly showed the intention of the higher-layer universe to lend their help and save our universe.
We admire this noble idea, therefore we have designed this System, in order to repay the kindness of those who bring salvation upon us, as much as we possibly could.

The purpose of this System is to spread Project Tetra even further,
As well as to observe the neighbouring universes as they bask in the coming salvation [Normal output failed. Error Code: 0x0ff00a77843 Please contact the system administrator.]

≪! Attention !≫
The message can only be send from a higher-layer universe to a lower-layer universe.

≪About the Possibility Universe Address≫

The address of a Possibility Universe is formatted as below:

①     ②       ③
UXXXX-XXXXXXX-XXXXXXXXX

① The Possibility Depth Layer where this System currently resides.
   This number increases every time this System is passed down to a lower universe.
② The serial number of the Main Coordinates.
③ The serial number of the Subset Coordinates within the Main Coordinates.

The differences between the Possibility Depth Layer, the Main Coordinates serial number, and the Subset Coordinates serial number, show the extent to which the possibilities of two universes differ.

≪! Important !≫
[HEAVILY CORRUPTED TEXT]

Corrupted text:

Uncorrupted text:

I feel that most of the corruption in this paragraph was added manually, but one sentence stands out as a typical Mojibake（文字化け） , which occurs when displaying UTF-8 encoded text in Shift-JIS:

Unfortunately, mojibake is not completely reversible, but chucking this into a mojibake inverter revealed an almost coherent sentence:

To solve the rest of the content, firstly converting the corrupted text into hex:

e3 81 93 e3 82 8c e4 bb a5 e5 a4 96 e3 3f e7 b6
b4 e3 82 8a e3 3f e8 80 3f 81 88 e3 82 89 e3 82
8c e3 82 8b e3 81 a0 e3 82 8d e3 81 86 e3 81 3f

Shift-JIS uses one or two bytes to represent one character (Shift-JIS lookup table), whereas UTF-8 uses variable number of bytes. However:

• knowing the original text is probably all in Japanese, there should be 3 bytes per character in UTF-8, and the first four bit of each character should be 0b1110 = 0xE.
• 0x3F in Shift-JIS is the question mark, which represents a character not found in Shift-JIS, so it could represent either one or two unknown bytes in the original text. Also 0x3F would not occur in any bytes in UTF-8, as the bytes should begin either with 0b1110 = 0xE (first byte), or 0b10 (subsequent byte).

This led to me dividing the hex up in threes, and replacing 0x3F with one or two missing bytes as appropriate. Let’s also fill in the characters deobfuscated by the mojibake inverter:

e3 81 93 こ
e3 82 8c れ
e4 bb a5 以
e5 a4 96 外
e3 ?? ??
e7 b6 b4 綴
e3 82 8a り
e3 ?? ??
e8 80 ??
?? 81 88
e3 82 89 ら
e3 82 8c れ
e3 82 8b る
e3 81 a0 だ
e3 82 8d ろ
e3 81 86 う
e3 81 ??

More observation: characters beginning with 0xE3 represents Unicode code point U+3???, and is likely a hiragana. The one beginning with 0xE8 is a kanji.

Now, guess work:

• ?? 81 88: The only sensible first byte would be 0xE3, which results in the Hiragana え. Other 0xE? yields very uncommon characters.
• e8 80 ??: The only possible range of characters is U+8000 to U+803F: 耀 老 耂 考 耄 者 耆 耇 耈 耉 耊 耋 而 耍 耎 耏 耐 耑 耒 耓 耔 耕 耖 耗 耘 耙 耚 耛 耜 耝 耞 耟 耠 耡 耢 耣 耤 耥 耦 耧 耨 耩 耪 耫 耬 耭 耮 耯 耰 耱 耲 耳 耴 耵 耶 耷 耸 耹 耺 耻 耼 耽 耾 耿. From the context I think the only sensible one is 考.
• e3 81 ??: This is the last hiragana in a sentence that seems to be a question, so I guess this is か.
• e3 ?? ??: From the context, I guess these hiraganas are の and は. The second hiragana cannot be を, as it would have been represented by e3 82 92, and 8292 is a valid character in Shift-JIS (a full-width lower case r), so it can’t have been converted to a question mark.

Which gives:

e3 81 93 こ
e3 82 8c れ
e4 bb a5 以
e5 a4 96 外
e3 81 ae の
e7 b6 b4 綴
e3 82 8a り
e3 81 af は
e8 80 83 考
e3 81 88 え
e3 82 89 ら
e3 82 8c れ
e3 82 8b る
e3 81 a0 だ
e3 82 8d ろ
e3 81 86 う
e3 81 8b か

There we have it:

这是在这个正在毁灭的世界的一角，我的自言自语
我们的宇宙，注定即将消亡
其元凶……没错，一定是“他们”

一切都从一条消息开始

这条来路不明的消息被保存在这张碟片上，至于其来源、送信者，我一概不知

不知道也是理所当然的，毕竟这条消息来自另一个宇宙
是从在我们的宇宙之上的宇宙——上层宇宙而来的

消息的内容着实令人惊讶

在我们的宇宙上一层，还有更多宇宙
在我们的宇宙的同一层上，有其他的可能性宇宙（！）
以及，这张碟片能让我们看到同层的可能性宇宙

然而，碟片所展示的光景是——
其他世界被“他们”污染、侵蚀、毁灭的模样

周围的宇宙，一定都是
因为“他们”，才变成了那样

当我意识到这一点时，“他们”已经在我们的宇宙之中

我们无法继续摆弄这条消息了
也就是说，已经不会有人听见我们的声音了
我们所能做的，只有注视着将这条消息传给更下层的宇宙

但愿这条消息能被“他们”所不在的宇宙收到

在“他们”——“秘封俱乐部”毁灭所有宇宙之前

……可是，我们其实明白。

当你收到这条消息的时候…早就为时已晚。

下一个宇宙里也会发生同样的事情吧。

周围的宇宙全都早就被污染了。

毕竟，这条消息本身就是送给“秘封俱乐部”的，不是吗？

那么，我们已经也被污染了，已经无法想象没有“秘封俱乐部”的宇宙。

谁知道最初制作这条消息的人究竟在想什么。

啊啊，干脆

传诵吧！

传诵出去吧，让秘封俱乐部到达更多更多更多更多宇宙吧！

扫描 BK 上 QR 码会打开一个秘密网页，其源代码中有指向另一个秘密网页的线索。后者有第一轨的无损版本（即 Activity-log-21-12-12），解释了为什么秘封组有三人，却叫 Tetra 计划（你就是第四人）。

根据 BK，全文都是梅莉 = Merami 读的。

顺便，背景音乐听起来很像《裸体歌舞》（想起『ジムノペディが終わらない』……害怕）。

• U0000-0000000-000000000: 秘封俱乐部从此向下层宇宙发布消息。
• U0001-9134845-120368896: 消息到达前受到极大干扰，因此该宇宙误认为上层宇宙的人会救赎自己（因为听到「あなたの助けに」（帮助你），以及只听到「掬い取って」（捞起）这个词的前半部分，也就是「救い」（救赎））。该宇宙随之创建了传播 Tetra 计划的系统，以报答救赎者。该系统可以扫描同位其他平行宇宙。
• U7730-■■■■■■■-■■■■■■■■■: 烧焦的信来自这个宇宙。该宇宙的人目睹邻近的平行宇宙接连死去，并认为秘封俱乐部就是毁掉宇宙的元凶，于是写了信警告下层宇宙，不过其实深知这都是无用功，不如破罐子破摔把 Tetra 计划继续向下传播。
• U7731: 这是我们所在的世界层，因为系统只能扫描到同层宇宙。专辑中所有 U7731 开头的曲子都来自与我们同层的平行宇宙。以及 Tr. 10 开头大概是原曲粉碎机 RD 少见的非常接近原曲的改编了，所以猜测这首曲子所在的宇宙可能就是东方 Project，以及我们，存在的宇宙。

本系统是为最崇高的计划设计的。
本系统构造复杂，旨在观测可能性宇宙，并传播神圣的信息。

本系统运行时，会取得系统目前所处宇宙的可能性深度层及可能性坐标。
其后，它会收集同一可能性深度层上的相邻可能宇宙的状态，并输出这些宇宙的信息。

≪本系统的存在意义≫

我们 U0001-9134845-120368896 宇宙，在 20■■-12-12 这一天，收到了来自上层宇宙的消息。
虽然这条消息支离破碎，但它清楚地显示了上层宇宙向我们伸出援手、拯救我们的宇宙的意图。
我们敬服其崇高的理念，因此设计了本系统，以尽可能地回报那些给我们带来救赎者的恩情。

本系统的目的是为了进一步推广 「Tetra 计划」。
同时也是为了观察邻近的宇宙沐浴在即将到来的救赎之中的模样[正常输出失败。错误代码：0x0ff00a77843 请联系系统管理员]

≪! 注意事项 !≫
只能从上层宇宙向下层宇宙发送消息。

≪关于可能性宇宙地址≫

可能性宇宙的地址格式如下：

①     ②       ③
UXXXX-XXXXXXX-XXXXXXXXX

① 本系统目前所在的可能性深度层。
   该数字在系统被传递到下层宇宙时增加。
② 主坐标序列号。
③ 主坐标中的子坐标序列号。

可能性深度层、主坐标序列号和子坐标序列号之间的差异，显示了两个宇宙的可能性的不同程度。

≪! 重要事项 !≫
[严重损坏的文本]

乱码：

原文：

最后这段大多乱码应该都是手动加入的，唯独有一句话很明显是日语乱码（Mojibake，文字化け），是试图用日本独有的 Shift-JIS 显示 UTF-8 编码文本时产生的现象：

乱码不是能完全逆转回去的，不过随便送到一个解码器网站里，得到了几乎能读懂的句子：

为了解读问号部分，首先将乱码文转写成 hex：

e3 81 93 e3 82 8c e4 bb a5 e5 a4 96 e3 3f e7 b6
b4 e3 82 8a e3 3f e8 80 3f 81 88 e3 82 89 e3 82
8c e3 82 8b e3 81 a0 e3 82 8d e3 81 86 e3 81 3f

Shift-JIS 用一个或两个字节表示一个字符（Shift-JIS 对照表）。而 UTF-8 用的字节数可变，不过：

• 因为原文应该全是日语，所以 UTF-8 里每个字符都会用三个字节，并且每个字符开头四个比特都是 0b1110 = 0xE.
• Shift-JIS 里 0x3F 是问号，代表 Shift-JIS 里没有的字符，所以可能对应原文中一个或者两个字节。另外 UTF-8 中不可能出现 0x3F，因为 UTF-8 字节开头要么是 0b1110 = 0xE（第一个字节），要么是 0b10（后续字节）。

因此可以把 hex 三三分组，并将 0x3F 以一个或两个未知字节代替，然后加上刚才解码器解出的部分：

e3 81 93 こ
e3 82 8c れ
e4 bb a5 以
e5 a4 96 外
e3 ?? ??
e7 b6 b4 綴
e3 82 8a り
e3 ?? ??
e8 80 ??
?? 81 88
e3 82 89 ら
e3 82 8c れ
e3 82 8b る
e3 81 a0 だ
e3 82 8d ろ
e3 81 86 う
e3 81 ??

又注意到：0xE3 开头的字对应的是 Unicode 代码点 U+3???，所以很可能是平假名。0xE8 开头的则是汉字。

现在开始猜：

• ?? 81 88: 第一个字节只可能是 0xE3，得到平假名「え」。其他 0xE? 对应的都是非常罕见的字符。
• e8 80 ??: 只可能对应 U+8000 到 U+803F 之间的字符: 耀 老 耂 考 耄 者 耆 耇 耈 耉 耊 耋 而 耍 耎 耏 耐 耑 耒 耓 耔 耕 耖 耗 耘 耙 耚 耛 耜 耝 耞 耟 耠 耡 耢 耣 耤 耥 耦 耧 耨 耩 耪 耫 耬 耭 耮 耯 耰 耱 耲 耳 耴 耵 耶 耷 耸 耹 耺 耻 耼 耽 耾 耿。联系上下文，这个字只可能是「考」。
• e3 81 ??: 问句最后一个假名，猜是「か」。
• e3 ?? ??: 联系上下文，这两个平假名分别是「の」和「は」。第二个平假名不可能是「を」，因为那样的话 hex 会是 e3 82 92，而鉴于 8292 是 Shift-JIS 里存在的字符（全角小写 r），所以不会变成问号。

于是得到：

e3 81 93 こ
e3 82 8c れ
e4 bb a5 以
e5 a4 96 外
e3 81 ae の
e7 b6 b4 綴
e3 82 8a り
e3 81 af は
e8 80 83 考
e3 81 88 え
e3 82 89 ら
e3 82 8c れ
e3 82 8b る
e3 81 a0 だ
e3 82 8d ろ
e3 81 86 う
e3 81 8b か

结果如下：