This images don't belong to me. I liked the artist but their Pixiv account was suspended / deleted so uploading this art here to presreve it. First time ever uploading so if there is any mistake please let me know
Yeah, you cannot apply the "AI Generated" tag directly. Instead, you put it (i.e. "AI Generated", just like this, NOT "AI image set" or anything like that) into the title and wait for the system to see this and apply the tag for you. The implementation is a bit odd...