6HP - Six Hearts Princess - Six Heart Princesses - All Princess Transformations (シックスハートプリンセス)

What the hell is this show? Best explainer here: The History of Six Hearts Princess

Post-apocalyptic Precure Hakkenden by Takashi Murakami and Studio Poncotan. Never officially released in English, aired only once on Japanese TV and never released on discs. You can get the fan-translated episodes on your favorite anime torrent tracker.

Seven episodes have been released, at the time of writing this. 15 episodes are planned in total, but the production stopped after 2019 due to the pandemic and may or may not resume in 2023 after the release of Takashi Murakami's "Mememe no Kurage 2", depending on circumstances.

This is a henshin collection from the show, the cleanest available versions:

Pink Princess transformation from episode 3 (ep. 1 version might be a bit too risque for YouTube).
Blue Princess transformation from episode 3.
Yellow Princess transformation from episode 5.
Purple/Green/Gold Princess transformations from episode 4.

Black Princess doesn't have a proper transformation scene as of right now.

Yes, this franchise started with that reasonably well-known Pink or Black song performed by Hatsune Miku for a cosmetics ad.

Index:
0:00 Pink Princess
0:41 Blue Princess
1:24 Yellow Princess
2:11 Green, Gold, Purple Princesses