Misora is Kazumi's best friend, and they are shown to be extremely close, despite Kazumi often getting annoyed or frustrated with Misora's overactive behavior. Kazumi has always been determined to protect Misora, being as she describes herself as being more 'level-headed' than the said best friend. She broad ends this promise to protect her when they are faced with the situation they were forced in.
In Chapter 1 when Kazumi finds Misora on the piano, they greet each other with a hug, then continue on their way, looking for their friends and a possible exit from the school. Misora appears to be very clingy to Kazumi in this chapter, as if she knows her fate.
It is shown that Kazumi has feelings for Ryuu right from the start, being as he first made his appearance, she blushed and stuttered, losing her calm, cool demeanor. They appear to be very good friends, too.
When they meet in Chapter 2 after Misora's death, Kazumi immediately hugs him and sobs into his shoulder as he does the same, both glad he found her, but at the same time extremely distressed, due to have lost his younger sister.
In Chapter 4 when the story then focuses on Kazumi and Ryuu reuniting with the others, it is then shown that Ryuu, too, has romantic feelings for Kazumi. Neither of them admit their feelings, however, due to being too caught up in the situation they were in.
At the near end of Chapter 5 when they are both seen in Akita Academy, Kazumi is staring out the window, supposedly sobbing to herself. Ryuu is there at the door frame, when he admits his feelings to her. He says all kinds of romantic things. Then, they kiss.