I have acne and dark circles. ..i am 20 years old girl. I want to use kojic acid from vitamins company USA. Would that be safe??

I wouldn't. If you use a depigmenting cream (and this stuff isn't a vitamin), you risk disfiguring yourself. It probably won't touch the dark circles. You need to manage your acne like the adult that you now are. You can do it. If topical benzoyl peroxide has not cleared you in two weeks, your physician can give you prescription-strength Rx to add. Be mature and discerning. Best wishes.