If you're looking for manga similar to Doukyonin no Bishoujo ga Lesbian Datta Ken., you might like these titles.
As a gay couple living in Japan (where gay marriage is not yet legal), Yuta and Kyota have found a unique loophole in order to live together and support one another financially, legally and medically; Kyota adopted Yuta. This nonfiction manga depicts how they met, living together, discussions with their parents, and their future anxieties and determination as they strive for independence and equal rights under Japanese law.
At age 30, Shou Arai came to a realization; they had no gender. Now they were faced with a question they'd never really considered: how to age in a society where everything is so strongly segregated between two genders?
Nonbinary manga artist Poppy Pesuyama is excited when forms offer the option to choose “neither” for gender and thrilled about their new job working as an assistant for mangaka X! But then he sexually harasses them, treating them first like a girl and then like something less than human. It only lasts a few months, but in some ways it never ends. Born into a body they hate and still reeling from the abuse they faced seven years ago, Pesuyama begins to rail at their past, their friends, and even their mother as they try to come to terms with who they are and what happened to them.
Sachiko and Kai have been together for quite a while now, and it's been some time since Kai's gender affirming surgery in Thailand. While they're by all means a happy couple on the outside, the cracks are starting to form on the inside. Their not-so-perfect relationship must now weather the storms of mismatched sex drives, dishonesty, Sachiko's concerns over her lesbian identity, and even a surprise marriage proposal gone wrong. Are they truly happy with one another, or will one of them stray?