Kazuki

I have never grown quince from seed, so good luck on that. Might I suggest that maybe if you had a friend or something with a quince, you can always take a sucker from the quince, because that would be much easier. Many of the nursery quinces also have suckers growing on them already. just dig down into the pot or ground and twist wire around the sucker tightly and cover it back up with soil. in a couple of week to months, dig it up again, and you will see that there are new roots right under the wire.

hope this helps