Wow I might have to eat humble pie. Koto not only did the best in the cooking even if she did the easiest thing. She wanted to help her mom cook so she could get better. Character growth at its finest.
Right? After your first comment I was thinking, "How is the author going to move past Koto? They obviously can't keep harping on how deficient she is, but they can't just make her suddenly start being functioning either."
And here I think the author handled this excellently. Koto is still Koto, but she actually does better than everybody else. Not because she was magically more competent, but because she was given goals that she could reach, and she reached them. In fact, her food was the highlight of the meal! And because of this achievement, she feels confident to push her boundaries a little further with helping her mom cook.
The way I see it being laid out in this manga, skills require experience. You can't simply wake up and be good at them. And this is the underlying issue with Koto's old relationship with Mariya: since Mariya did everything for Koto, Koto never got any experience doing those things herself, and completely fell apart when they parted ways. Even when Mariya came back into her life, Koto fell apart immediately after anyways, because Mariya was still doing the hard part of maintaining consistency for Koto.
