Yesterday, the eden* visual novel got mistakenly released on Steam. The game's publisher called MangaGamer (which also sells other visual novel games on their own online store) made an announcement about the release mistake and is trying to contact Valve. Although the game is still up on sale possibly as a pre-order. Current price is discounted to $9.99 or ¥1134.24 instead of $19.99 or ¥2269.62. Check out the store page for more details.
Update: *eden is no longer available for sale.