Oh, interesting. I noticed that the results board in Hiiragi's flashback is for Seirin Academy, the one Tsubaki said had "cute uniforms." I wonder if she failed to get in, despite being academically strong and getting a medal for kendo, which prompted her "useless" comments. Or maybe she got in, and Hiiragi didn't, and Tsubaki said something along the lines of being okay with turning down Seirin and going to whatever school Hiiragi got into because she would be "useless" without Hiiragi. Hiiragi may have thought Tsubaki was being flippant, while Tsubaki truly believed she couldn't do anything without her sister by her side. Whatever the case, communication is key here, girls.
I really like Ningiyau's writing. Often dropping in little story threads amidst all the silliness. It flows so smoothly.