Grace is a web novelist / fanfic writer. This image was used on his doujin novel distributed at Comiket 79. Possibly this image was drawn by his friend.
Not pixiv's fault; Danbooru's method of creating the source link is just too simple. It just takes the number at the end of the URL (125384) and sticks it to the end of http://www.pixiv.net/member_illust.php?mode=medium&illust_id=. But novel images use a separate list of IDs than other pixiv images, so the link isn't right.