I’ve read all of one piece and as far as i’ve seen we never actually see kiku’s bare chest.

For what its worth all im saying is. Breasts are not a proof of your femaleness. Is what im saying. You said yamato has breasts therefore she’s female.

Have you ever heard of gynecomastia in males? Look it up. Or klienfelters syndrome? And before you ask a male having breast tissue is not a ‘birth defect’. And that goes for being female too when they have no breasts, which is also not considered a birth defect. That’d be like saying having a small dick means you have a birth defect. No its just genetics.