Rate this episode here.

I feel it makes a lot more sense than many would think. Aya is another victim of trauma and abuse lasting her whole life. While she was able to get glimpses of the outside world (also helped she was able to get a lot of books), her life was pretty much dominated by Akio's depraved dominion over her.

What she's doing is drastic, but it's basically her way of making a fresh start, forgetting about that past and basically letting what she's been holding in flow free without restriction. It of course helps that she has her mom and brother now, and also of course her true "knight in shining armor" Kabane to fawn over (I guess she transferred that ideal from her brother onto him)

It's not that she feels responsible for what Akio did, it's that she only exists because of it. Do you ever read/watch Game of Thrones? Cat hated Jon from the day Ned brought him home because he was a living embodiment of his infidelity. She didn't hate Jon because she blamed him for Ned cheating on her, she hated him because he reminded her that Ned cheated on her.

Similarly, Aya was worried that every time Shiki or even her own mother looked at her, they would just remember what Akio put Kumi through to make her. She didn't want to be a traumatic trigger to her family.

It's worth pointing out that despite spending most of her life locked in a basement wanting to die she's a functional member of society, even more than Kon.

I didn't see her reasoning for blaming herself for what the uncle did, but I don't need logic to appreciate the "will you accept me" scene. Very sweet, despite being so a short scene.

Look at what you made do, this hurts me more than you, why are you such a naughty girl, your mom is sick because of you.

There are a lot of abuse classics which work well, when repeated often enough and especially well on a young, impressionable mind. Aya is smart enough and a strong will, so she realizes it on a logical level, but it still leaves mental scars and she's in emotional turmoil in this episode, so her ability to reason was a bit weak and her mental defenses faltered.

Aya is probably the most mature of the kids despite being the youngest. In her situation and environment, she had to grow up fast or she wouldn't have survived.