We regret to inform you that Princess Project will soon be made unavailable for purchase due to a request from viviON, the owners of the Triangle! circle. To ensure that everyone has a chance to pick it up while it's still available, we've decided to heavily discount the game on all available platforms, so make sure to get it before it's gone! Thank you for your support and understanding.
From the company viviON (Triangle!):
販売終了の理由につきましては、
「社内の体制変更に伴い、充分なサポート環境が提供しにくくなったため、提供の終了を決定いたしました。」
https://store.steampowered.com/app/1106080/Princess_Project/