eltonlin
The sentence --> into flashcard is exactly what I was hoping for. If this is high quality I'd happily pay $60/year (something comparable to what I pay AnkiApp pro / Univerbal subscription).Here's some feedback so you can consider if you want to invest.

I tried the app but on the first few attempts it gave an error 404 in console.

The example long paragraph I put in from an email gave me only 4 flashcards, two of them was on Arigatou, when I wanted to focus on the other words: ショップからの回答: [Re] 947912984 につきまして ご連絡ありがとうございます。 ご返送のお手配、誠にありがとうございます。 ご返送品が到着いたしましたら、再度ご連絡致します。 この度は、お手数、ご迷惑をお掛け致しまして誠に申し訳ございません。 恐れ入りますが、よろしくお願いいたします。

Also I couldn't figure out the UI initially, it took me like 10 seconds to think to try the "chat" feature to input into the LLM.