The puzzle itself is interesting, but it took a long time to reach 20,000 yen. Also, when I tried to redeem it, a mission came out and I had a mission to see the advertisement 150 times. I felt like I was still looking at it little by little, but even if I saw it once, it wasn't counted. Selling watermelons is counted, but ... I will add it again if I actually get it.
You can easily save up to 10,000 yen, but then the amount will gradually decrease, and by the time you exceed 18,000 yen, you will only get 1 yen no matter how hard you try. Even if I finally save 20,000 yen, I don't think I'm willing to pay because I'll be sending out missions such as seeing advertisements 150 times, making some watermelons, and so on.