project raputa

project raputa is an ARG connected to the sasakure.UK Area (sasakure.UKちほー) in maimai でらっくす BUDDiES. It is crucial to unlocking the hidden songs of this event.

Unlock process

After completing sasakure.UKちほー, the TJ.hangneil Area (TJ.hangneilちほー) is opened. This Area includes the unlockable songs ozma and 神威, the latter as a Perfect Challenge.
Equip the nameplate sasakure.UKちほーその3 and the frame TJ.hangneilちほー, obtained through the respective Areas, to reveal a message in Japanese Braille where the two meet. When deciphered it reads 39 339COMBO. Play either the Standard or DX charts of 39, and have a maximum combo of exactly 339, and you will receive the nameplate 宇宙旅行券 (Space Travel Ticket).
Prior to the event, the project raputa official Twitter account posted this video, which features lines extending from the letters "sasakure.UK × TJ.hangneil" moving up and to the left. Taking the strings "sasakureuk" and "tjhangneil" on a standard QWERTY keyboard, and moving upward and leftward until reaching the number line, produces the numbers 2121874378 and 5761656389 respectively. Multiplying them together produces the number 12225511066659101042. If this number is entered as a serial code on maimai-net, the player receives the icon 旅行スタンプ(月面基地) (Travel Stamp - Moon Base).

Part of the 宇宙旅行券 nameplate, with all 5 titles superimposed. (Credit to rN)

Equip both the nameplate and icon received above, and the Moon Surface Area (月面ちほー) will appear. This Area contains the unlockable song 月面基地, as well as five titles with five-character codes: SHTRB, EAEKE, EWBMA, ABINO, and ◤MHTO.
The 宇宙旅行券 nameplate has a 5-by-5 set of spaces on its left. Place all five codes in it, top to bottom in the order they are received in the Area. A yellow line passes through all of these characters, and the ◤ character indicates the direction of the line - the order in which they should be read. Following the line, starting from the top right, reveals the message BREAK THE MOON BASE WITH B.E.A.M..
Play 月面基地's charts in the following order: BASIC, EXPERT, ADVANCED, MASTER, by hitting all BREAK notes and nothing else. The player receives the icon 旅行スタンプ(???) (Travel Stamp - ???).

Equip this new icon and the Dark Side of the Moon Area (裏月面ちほー) will appear. This Area contains two Perfect Challenge songs: Apollo, and the new song raputa.
At the end of this Area, the title project raputa completed is obtained, signalling the end of the ARG.

A development interview by 佑 and あまくちジンジャー about the development of project raputa can be found here.