This has been hinted like ten chapters ago.
What a 4D chess move by Hinata, now Sanae can't pay attention to her because she will be distracted with Yuri kissing her all day long.
I'd like to remind of all of you that there's a counter in the end of each chapter, and we're nine months away from the end of the story. This is just a footnote to give depth to Umimi's character, nothing else.
I will allow myself to have hopes for something spicy to happen, although I would prefer it if it were with Shizuku instead, tbh. Sorry Umimi, you don't have that bitch energy Shizuku has and infatuates me.