In Japan, while same-sex marriage remains unrecognized at the national level, several municipalities have implemented partnership certification systems for same-sex couples. A nationwide online survey conducted by researchers at the University of Tsukuba revealed that these systems do not correlate with improved mental health outcomes for sexual and gender minorities (SGM). The study utilized data from 2022 and assessed psychological distress and suicidal ideation among participants. Results indicated that SGM individuals experienced significantly higher psychological distress and suicidal thoughts compared to their cisgender heterosexual counterparts. Surprisingly, those living in municipalities with partnership systems reported higher rates of suicidal ideation. The findings suggest that while SGM individuals in Japan face considerable mental health challenges, the existence of municipal partnership systems alone is insufficient to enhance their mental well-being. The study calls for more comprehensive civil rights protections and policies to effectively support the mental health of SGM individuals in Japan.