Hi Takuya Matsuyama,
This is a wonderful app and I would love it even more if it was possible to buy the app permanently!
Even if the permanent license was around 200$ I wouldn’t hesitate to buy it, so please consider this as an option. I have never been a fan of subscription services and it would be sad if that is the only reason not to use this app.
Keep up with the great youtube videos and have a nice day!
With best regards