The artist's account has been suspended, don't know it's decided by artist himself/herself, or banned by Pixiv due to break the rule. Although before the account suspended, the artist delete all the previous works.
Here is a series works I saved, with title 首輪生活(The Life with Collar), which has wonderful concept and beautiful atmosphere. I was wondered that if there is a master orders these yuri slaves only dressing school swimsuit to live, and without any underwear. And order them to training each other every day.
Fucking sucks that the Pixiv account is suspended. Happens way more often than you might think, I've often made the mistake of bookmarking something "for later download" and then it's gone when I check back.
You're right that this concept is hot, makes me wonder what else he might have uploaded to his profile.