Recently, in Japan, adultery allegations against a young congresswoman were widely reported.
The woman in question used to be a member of the very popular pop group, “Speed”, but is now a single mother of a son with a hearing disorder, and a member of the House of Councilors.
Last month, one magazine reported suspicions of a love affair between her and a man in Kobe City Council.

In the magazine, there was a picture of her holding hands with the male city councilor while sleeping on the Shinkansen (Japanese bullet train), and according to the magazine, they spent two nights together at her mansion and a hotel.

She admitted her 2-night stay with him, but she emphasized that as he was now in the process of a divorce mediation procedure against his wife, she did not cross a line. "Not crossing a line" indicates that there is no sexual relationship between them so far.

Why did she say "I have not crossed the line?"
Is there any legal significance here?
I do not know the truth (only the two people involved would know this), but let me consider this from a lawyer's point of view.

According to reports, the city councilor has been married and has two children. However, according to him, his marital relationship broke down 5 to 6 years ago, and they began to live separately since the summer of last year, and (as already mentioned) are currently following divorce proceedings.

Under Japanese family law, a husband and wife can divorce by mutual agreement, but if the agreement does not hold, the court can order a divorce only due to the following:

1) An act of adultery.
2) If one party was abandoned by the other in bad faith.
3) If it is not clear whether a spouse is dead or alive after at least three years.
4) In the event of severe mental illness.
5) In the event of a grave cause that deems continuation of the marriage difficult.

Additionally, according to the judgment of the Supreme Court, a divorce claim from the party who caused the failure of the marriage by an act such as adultery, is rejected.
In other words, for example, if a couple has already been separated for a long period of time due to the husband's adultery and it is determined that there is a grave cause that makes the marriage difficult, the husband's divorce claim will be dismissed. This is known as “the theory of the spouse who caused the break up”. Because of this, I guess the councilors couldn’t admit a sexual relationship.

Of course, in this case, because the man has already began to live separately from his wife and insists that the marital relationship has already broken down, there is a possibility that any current case of adultery did not cause the collapse of the marital relationship. However, according to the report, the wife claims that their marital relationship has not yet broken down and argues that he only unilaterally began separation. Therefore, his assertion that the relationship with the congresswoman started after the collapse of the marital relationship might be denied. Considering this risk, maybe they could not admit to a sexual relationship.

By the way, since they were holding hands while sleeping on the Shinkansen and spent two nights together, it would be normal to assume that a physical relationship exists. If so, does claiming that "a line has not been crossed" become disparaging to their honesty?

My guess is as follows:

First of all, we have to know that Japanese judges tend not to recognize the fact of adultery unless there is direct evidence. This is because Japanese judges know well that the theory of the spouse who caused the break up is often actually unreasonable. In general, many cases to which the theory is applicable have continued for a long time, and the marital relationship completely collapses. Therefore, if the judges do not intervene, only an unproductive, negative relationship remains. Thus, the Supreme Court has decided to make an exception to the theory. They stated that:

If the claim is from a spouse who caused the break up, but the separation period is comparable to their age and their cohabitation period, with no children involved, as long as the judge does not recognize any special problems that would result in unfair events due to divorce, such as one party suffering mental, social or financial hardship, the judge cannot deny the claim because it is from the spouse who caused the break up.

However, since the hurdles required by this court judge are high, the theory continues to bring disagreeable results. Therefore, my guess is that judges do not want to get too involved with, or admit too much about the fact of adultery.

Currently, a review of family law is also being discussed in our country. One idea is that if a household exists separately for a certain period of time, regardless of the cause of separation, divorce is granted.

In my opinion, such thought is more appropriate than the theory of a spouse who caused the break up.