Article 819Person Having Parental Authority after Divorce or Acknowledgement of Paternity
第八百十九条（離婚又は認知の場合の親権者）
If parents divorce by agreement, they determine in that agreement that both of them or one of them is to be the person with parental authority.
父母が協議上の離婚をするときは、その協議で、その双方又は一方を親権者と定める。
In the case of a judicial divorce, the court determines that both of the parents or one of the parents is to be the person with parental authority.
裁判上の離婚の場合には、裁判所は、父母の双方又は一方を親権者と定める。
If parents divorce before the birth of the child, the mother exercises the parental authority; provided, however, that the parties may agree for both parents or the father to be the person with parental authority after the child is born.
子の出生前に父母が離婚した場合には、親権は、母が行う。ただし、子の出生後に、父母の協議で、父母の双方又は父を親権者と定めることができる。
Parental authority over a child whose paternity has been acknowledged by the father is exercised by the mother; provided, however, that the parents may agree for both parents or the father to be the person with parental authority.
父が認知した子に対する親権は、母が行う。ただし、父母の協議で、父母の双方又は父を親権者と定めることができる。
If an agreement as referred to in paragraph (1), paragraph (3), or the preceding paragraph is not reached or discussions toward such an agreement cannot be held, the family court may issue a ruling to stand in place of such an agreement, at the request of the father or the mother.
At the request of the child or the child's relative, the family court may change the person with parental authority, if it finds it to be necessary to do so in the interests of the child.
子の利益のため必要があると認めるときは、家庭裁判所は、子又はその親族の請求によって、親権者を変更することができる。
In a judicial decision under paragraph (2) or the preceding two paragraphs, when deciding whether to determine both parents or one parent to be the person with parental authority, the court must consider, in the interests of the child, the relationship between the parents and the child, the relationship between the father and the mother, and all other circumstances. In this case, when any of the following applies, or when it is otherwise found that determining both parents to be the person with parental authority would harm the interests of the child, the court must determine one parent to be the person with parental authority:
when it is found that the father or mother is likely to cause harm to the mind or body of the child;
父又は母が子の心身に害悪を及ぼすおそれがあると認められるとき。
when, taking into consideration whether there is a risk that one parent will receive from the other physical violence or other words or conduct having a harmful effect on the mind or body (referred to as "violence, etc." in the following paragraph), the reasons why the agreement referred to in paragraph (1), (3) or (4) is not reached, and other circumstances, it is found to be difficult for the parents to exercise parental authority jointly.
In the case referred to in paragraph (6), in determining whether it is necessary for the interests of the child to change the person with parental authority determined by an agreement between the parents, the family court is to take into consideration the course of that agreement, subsequent changes in circumstances, and other circumstances. In this case, in considering the course of that agreement, the family court is also to take into account whether there has been violence, etc. from one parent to the other, whether there has been conciliation under the Domestic Relations Case Procedure Act or use of alternative dispute resolution procedures (meaning the alternative dispute resolution procedures prescribed in Article 1 of the Act on Promotion of Use of Alternative Dispute Resolution (Act No. 151 of 2004)), whether a notarial instrument was prepared concerning the result of the agreement, and other circumstances.