The game can’t be bought here. You can go to ci-en, fantia or dlsite to buy the game. Just google it
Viewing post in Syahata's bad day(v1.0.5) comments
You can use DLPay (https://dl-pay.com/) to buy DLsite points. Select the amount of points desired, than use PayPal to pay. Once finished, it will generate a Serial Code do redeem the DLsite points (https://www.dlsite.com/maniax/mypage/user/serial/point). Other option is to buy DLsite points from other 3rd party sites (Ex.: Tokyo Otaku Mode) were payments are broader (but the ratio price/points is higher).