When this image was uploaded to the Japanese Uncyclopedia, only four episodes of Toradora! had aired. Probably the original image was made before any of Toradora! aired.
The only Kugimiya role I can think of that had characters with uniforms like that would be Kataoka Yuuki ..but the similarities between her and the untagged girl are pretty sparse. I've been looking through a list of her roles and haven't turned up anything yet for the ones I've found pictures of.
Oh. But, uh. I have updated the source with a pixiv link and added the artist's tag, though. There seems to be a larger version of it there, but I figured uploading it could wait until this mystery is solved.
Eh? No, I suppose this exact version didn't come from there. I was just assuming that the artist's page would be a more accurate source than something like the Japanese uncyclopedia. Since the source field seems to be far more specific than I thought, my apologies. I've put the old source back.
Louise Françoise le Blanc de la Vallière (Zero no Tsukaima)Shana (Shakugan no Shana)Kurotsuchi Nemu (Bleach)HoiHoi-san (HoiHoi-san)Kagura (Gintama)Edelweiss (Dokkoida)Magami Megumi (Only you -Recross-)Alphonse Elric (Fullmetal Alchemist)Kamyu (Utawarerumono)Sanzen'in Nagi (Hayate no Gotoku!)Mimi (Mnemosyne)Kooh (Pangya)Rizel (Rizelmine)Minase Iori (iDOLM@STER) (Bokusatsu Tenshi Dokuro-chan)Nena Trinity (Gundam 00)Uematsu Koboshi (Pita-Ten)