It's this interview from way back last June... https://getnews.jp/archives/3299988
Bad Google Translation:
"I tried to draw what would happen if the person I liked was really close to me. I love the combination of opposite characters so I thought I'd make a duo that would never get along if they were normal. I also like Western music, so it's nice to have a relationship that connects through music. I also think about it, and it's a story that's packed with my own 'likes'." ...
"I don't really know if the manga I'm drawing is a so-called 'yuri'. There was a time when I was worried about my sexuality, and I am very happy that people of various sexualities, backgrounds, lives, and occupations will be able to see the stories and characters that are born from that. I would be happy if you could watch over Mitsuki and Aya warmly.'"
So she had been talking about putting a lot of herself in the story including romantic likes. The fact a story born from her perspective (including her sexuality) can be enjoyed by so many people makes her happy. She's not worried anymore. She's put herself into this and found people have accepted it beyond a "so-called" category and it's become a universally understood feeling. There's romance in the story and it's between Mitsuki and Aya. Her own publisher frames it like that for the book coming out.
In the months since she's drawn them moving in together in the future, on a holiday together five years down the road, matching couple accessories etc, and they fall very neatly into her "type" from previous manga. Her muse has been constant over the years and you see whispers of the two in her prior work. The change is people accepting it beyond the usual reach. That has to be such a great feeling as she puts a lot of herself into it.