Pixiv description:
http://www.nicovideo.jp/watch/sm17226263 】より。　しょこあ｢後部座席…バーンって飛んでくボタンとか付いてないのかな…｣　こうですか？わかりません。
【PR】
≪簡単ネット審査≫お急ぎの方、お悩みの方、初めての方でも大丈夫！

I would add this to the "Unlikely Crossovers" pool, but there's been quite a lot of touhous in gta...

The followup post to this one has the back seat ejecting from the car on rockets. Koa in the driver's seat must have gotten tired of Cirno asking "are we there yet?"

Just FYI: in the video above, they are (left to right): Kokoa, Shokoa, and Cirno in Hiragana and Koakuma in kanji. Any ideas what 'Shokoa' might mean?

Hyokai said:
Just FYI: in the video above, they are (left to right): Kokoa, Shokoa, and Cirno in Hiragana and Koakuma in kanji. Any ideas what 'Shokoa' might mean?

"Shoujo Koa" maybe?