She sang the infectiously cheerful OP for Hyakko, Suppin Rock, and had a bit part in the show too, if i remember correctly. I dun know much about her actually, besides the fact that she sang about B-cup bishoujo (bishojo? i can't remember which is 少女 or 処女). Seems to be a newcomer; after all, she is only a teenager still. (But a cute one nonetheless.)
Interestingly, Ogawa sported a giant afro in the PV for Suppin Rock, as can be seen in the bottom left of the pic. My first impressions of her some months ago were thus, "Hey that's a cool rebel rocker girl." After coming across this pic it's more like "moemoekawaii!!!" Amazing what changing hairstyles can do for one's image.
Random Note: Hirohashi Ryou kind of looks a bit too "normal" without her afro.