My cat has white bumps on its chin. Is it acne? How do I fix it?

Given the location of the white bumps on Kira's chin, it's most likely that this is a case of chin acne. Cats tend to develop this condition as a result of eating/drinking out of porous bowls, such as plastic or ceramic. While I don't know which type of bowls you're currently using, I would recommend using either stainless steel or glass bowls, taking care to wash them daily. This change should help minimize the chance of future recurrence. For now, you can clean Kira's chin with an antiseptic cleanser, like chlorhexidine (Hibiclens is one brand) twice per day. Be sure to rinse his chin after wiping with the cleanser! If the bumps persist in another week or two, or if they get worse at any point, then you'll need to take Kira to his vet for further evaluation. I hope that everything goes well!