YSK: If you are a parent in a joint custody agreement, don't trash the other parent or other side of the family while your child is with you, even if you think they can't hear you.
from /r/YouShouldKnow
YSK: 共同親権契約を結んでいる親であれば、たとえ相手に聞こえていないと思っても、子どもが自分と一緒にいる間は、相手の親や相手側の家族にゴミを出さないようにしましょう。