Sorry but direct card payments (stripe payments) are not currently available.
I would recommend :
a. create a paypal account and attach the card to it then pay (will pay from the card)
b. try purchasing from dlsite ( https://www.dlsite.com/maniax/work/=/product_id/RJ409479.html/?locale=en_US ) , after purcase follow the instructions ( https://nymphokyun.net/slavebar-nishys-futanari-birthday/ ) to uncensor the game (dlsite version is censored)
I hope this helps,
~NK