it is recommended to let it ripen for a few days at room temperature. Allergy to kaki is a rare condition, but nevertheless, some individuals are prone to it. The allergens found in persimmons are ...
Lastly, I'd like to offer a bit of advice. If you do happen to come across a persimmon, choose a ripe one with a large calyx. The less space there is between the fruit and the calyx, the better.