Unfortunately, same-sex marriage has not been legalized in Japan yet even though the number of countries legalizing the same-sex marriage has been increasing globally.
Therefore, a same-sex spouse is not applicable to any “spouse-related” visa status such as “Spouse of Japanese National”, “Spouse of Permanent Resident”. Even he/she cannot apply for Dependent visa status as a spouse of a work-related visa holder.
However, there is a possibility to bring your same-sex spouse if both of your countries legalize same-sex marriage and you and your spouse registers marriage officially and lawfully in each of your countries. The visa type is called as “non-prescribed Designated Activities (特定活動・告示外)”.
Also, through a lawsuit of a same-sax spouse legitimately married to a Japanese national in the US, the Immigration Office has granted “non-prescribed Designated Activities (特定活動・告示外)” to the same-sex spouse in March, 2023 even the same-sex marriage is not legalized in Japan.
“Non-prescribed Designated Activities (特定活動・告示外)” visa status is a special visa type granted based on considering each situation, so you should plan the application carefully before you apply for it.
If you want to consider it, go to the page below;