You know what I just realized?

The fact that both Sayo and Hina Hikawa have birthday on March 20th.

The fact that the First day of Spring is on March 20th.

And also, Sayo joined Roselia. While Hina joined Pastel*Palettes. Which both bands symbolized flowers.

Which means they BLOOM on their birthday!

But anyways, Happy Birthday to both Hikawa Sisters!