[She knows it won't be the same but Ai will offer up the same thing she has with her mother - the exchange of blood that brought memories and feelings too. It helps to not feel so lonely. At his words, Ai almost scoffs.]
Ren is ridiculous. I've been thinking of you before you were ever born. It was my idea first for mother and papa to have another child.
[Maybe Ai wanted to have a little sister to dote on and dress up (though she would not hesitate to do the same to her brother as well) but she was the one who wanted a sibling long before their mother did at least. And papa was only too willing to wait for her to be ready for it.]
I will always be you onee-sama.
[Whether she's older than him or not. At his question, Ai does push him back so she can look at him with a little frown.]
They're both here but you can't meet them looking like that! [Not with the orange jumpsuit.] I'm taking you shopping for something decent to wear.
[While it's true that the jumpsuit is absolutely terrible, Ai also has to prepare him for meeting their parents. She hefts her schoolbag higher up on her shoulder and moves to wrap her arm around Ren's. Then proceeds to start down the stairs so they can go to the store.]