From the article:
While only Episode 1 has been officially released, all 12 episodes have appeared on unauthorized torrent sites. The material appears to be finalized, including full animation and audio, though the source of the leak remains unknown.
One of the circulating torrent file descriptions includes a link to a Japanese streaming site, happydouga.jp, though its connection to the leak is unverified and may have been falsely added by the uploader.
Yeah, that actually surprised me the most here. The fact that all of it can leak at once seems like a good sign