Responses
That or they could be referring to adopting him so that they would be family. Here is a manga that mentions adopted marriages. http://www.mangago.zone/read-manga/ani_no_hanashi/mf/sa-c003/pg-7/
Honestly for me I thought they meant moving in together l(⌒▽⌒)
I'm confused about them talking about getting married in Chp 6, isn't gay marriage illegal in Japan? I think there are several city wards that will issue partnership certificates so is that what they're referencing?