they're real

I don't think sh actually agreed to marry Yashima. Yashima was just confused and remembering fragments earlier, but in pages 17 and 18 we see the full context of the conversation, when Sakano was just talking about her girlfriend and Yashima proclaiming Sakano gotta marry her. What they are saying is that they both want to be able to get married in the next era, but not to each other. In context, Yashima wants to find a boyfriend while Sakano wants Japan to legalize gay marriage.

I think of this as the proper context what the manga is trying to deliver.

I also hope that.. both Yashima san and Sakano san are able to get what they want in the next era