Very cute, but shouldn't it have the subtext tag? There's nothing really explicitly romantic here.
I thought the whole thing was very obviously romantic. It was a classic falling in love scenario.
Yeah, I guess you can say it's technically unstated, but the relationship is the sole focus of the piece, and feeling comes through very strongly, so to me it makes sense to tag it as yuri.
Both of them are just a little too eager to get closer. Remi got pretty flustered when Sayaka was taking her measurements, and the fact that she had to tell herself "nothing strange is happening" means something was definitely happening there. The last we see of the picnic isn't really Sayaka asking Remi out, but it's close enough; as they're lying next to each other, Sayaka asks Remi to stay with her while cupping Remi's face with her hand, and Remi says yes with her hand on Sayaka's hand.
So I don't know if they're going out by the end, but I think it's obvious how they feel about each other, even if they haven't admitted it to themselves yet.