【お題日記】大人の関係で“ルール”って必要？それとも自然に任せるべき？

what mean "自然に任せる" ?
Does that mean without contraception?
If you aremarried, that may befine — but given thephrase "大人の関係/'adult relationship'", I understand it to imply a connection outside ofmarriage. In thatcase, it should only be with apartnerwho can truly commit to taking responsibility if apregnancy occurs.
Taking responsibility meansguaranteeing the child's upbringing and education as aparent until theyreach adulthood —covering cramschool attendance, studying abroad,university enrollment, andeven graduateschool. If all of that can beguaranteed, thenperhaps forgoing contraception isacceptable. But if it cannot, birth control is thebareminimum.
As for other rules: do nottakewhat belongs tosomeone else.
If the otherperson ismarried, you should notpursue a relationship thatmonopolizes them or ispremised on divorce.
If you yourself aremarried, you should notpursue a relationship that wouldrequire dissolving thepartnership with your ownpartner.
A relationship conducted within these rules — that, Ibelieve, iswhat truly deservesto be called an "大人の関係/'adult relationship'".