Looks like a fill-in-the-blanks game. Akane must be saying those four sweet words Akari said to her:
I love you, onee-chan. I love you, onee-chan. I love you, onee-chan. I love you, onee-chan. I love you, onee-chan. I love you, onee-chan. I love you, onee-chan. I love you, onee-chan.