By Japan Times on 10/24/2018
\”… According to Japan’s Civil Code, a child conceived by a wife during marriage is legally presumed to be the child of her husband. Therefore, even if another man is the biological father, when the wife registers the birth, as she is legally required to do, the baby automatically enters her family register as the husband’s child. …\”
Read the entire article: https://www.japantimes.co.jp/community/2018/10/24/how-tos/husband-not-babys-father-can-child-take-dads-name/#.W-TIFK2ZOCR