The tag on the other pic in his pixiv does say Rin, but you know that we "tag what we see, not what we know" on Danbooru. I'll leave it up there for somebody else to decide on, but this is definitely not Rin as her hair is blonde and her outfit is much more traditional. She doesn't have detached sleeves, an ascot, or a hair bow, either.
Short version, he may have tagged her there, but I think it's for the sake of the meaning behind these pics. He was too vague for anyone to really say what that meaning is/was, though.
Edit: Btw, if somebody gets a chance to, will you please check the translations on these pics? I did use Google, after all.
