When I first started studying Japan’s legal system, one mystery was why people brought constitutional lawsuits they were clearly going to lose.
Now I understand; these lawsuits are a form of lobbying. The five cases before the courts challenging the constitutionality of Japan’s failure to recognize same-sex marriage are a prime example.
Japan’s Constitution articulates a panoply of rights, including some that are highly abstract and others, such as rights to education and minimum standards of living, requiring implementation through social welfare systems. Some rights are thus not actionable directly through the courts; they are considered mandates to the Diet, the nation's parliament, for implementation through legislation.