I did some tag editing, but I must admit that I can't distinguish the different Atelier games and their characters very well. Apparently the blonde girl is known as both Marie and Marlone, the one with the cylindrical hat is Elie and the one with the truncated cone hat is Anis. The "elfir" tag was put there by the uploader, perhaps that's what the artist is called. I also don't know whether the object being inserted is a test tube or a glass dildo or if it even matters.