Hey guys, AYhaz here.
Although I'm the only one who'll be sharing a piece of my mind about this BMS, I'm far from being the only one who partook in it.
What we have right here is... quite the mastodon.
There's quite the lengthy backstory behind it, so to make it short:
Aezlack and 黒皇帝 spent a couple hours mashing various motifs together in a Discord channel we have over here in BMS Community (called #producers); I didn't actually get wind of all this until it was over, and decided that, well, things couldn't end with a mere 0:19 clip. So I shaped what the two of them made into a full-fledged song. But that's not where the collaboration aspect ends; I gathered as many western charters as possible and asked them to contribute charts. The result is a whopping total of 17 charts, as seen below:

LIST (5K):
[isocosa soflans you in many awful ways] ☆32 | obj. isocosa

LIST (7K):
[BEGINNER TIME] ☆2 | obj. isocosa
[7K BEGINNER] ☆4 | obj. Lollipop
[NORMAL FORM] ☆4 | obj. isocosa
[7K NORMAL] ☆6 | obj. Lollipop
[HYPER SPACE] ☆6 | obj. isocosa
[ANOTHER ONE] ☆10 | obj. isocosa
-@everyone's voice shall be heard- ☆11 | obj. wage's slave
[INSANE] ★5 | obj. w
[OOF] ★★2 | obj. Tristan97
[GOD] ★★? | obj. AXION

LIST (9K):
[can you hit these buttons] ☆49 | obj. agurin

LIST (14K)
[isocosa vs your hands] ☆11 | obj. isocosa

LIST (SPECIAL):
(VERY MIX) ☆10 | Another Mixed by Reprogram Girl
[LN] ◆11 | obj. w
the A-Men Brothers redesign ☆12 | obj. tdef
[ONE KEY] ☆? | obj. isocosa

As such, this BMS is the fruit of a collaboration between a bunch of western people.
We tried to offer as much variability as possible so that everyone who gets ippaitukuru2019 would find at least a chart or two they like among those 17.

The #GENRE field contains and invitation to our Discord, "BMS Community". Come say hi! We'll be glad to receive you.