In June, the foil English Hatsune Miku: Digital Sensations Secret Lair sold out in under three hours, with non-foil and Japanese versions following suit soon after
Grindstone is a consideration as another way to break Water Crystal, but is a bit narrow
This will be a full-scale competitive event, similar to the Flagship Battle, and like other events, players can apply to participate via Bandai TCG+
I'd hazard a guess that the majority of players who have been around for a couple years now have most of these cards already
Eventually, it would be unbanned as Commander a few years later when the Banned as Commander section of the banlist was abolished
These promos were only released in the Asia/Pacific market at Standard events, so they can be tough to come by in other parts of the world