Can I harvest seeds from a fresh tomatillo?

[HiPoha]

Rambler: Bulam is a korean type summer squash, it taste similar to a zucchini. It is a fast growing vine and the squash can be picked anytime five days after pollination. I got the seeds from Kitazawa Seed Co. The largest I let them grow is to grapefruit size, which is about ten days, after that the seeds inside gets hard.