"Most high school boys don't use one more than once a year."
No need to specify, "high school boys." Most people don't. Well, maybe it's more common in Japan.
Cleaning your nails is actually very important. Most of the bacteria on your hands are there.
"She put the cutting board and the onions where my hands can easily reach them all..."
Sounds very wordy for something so simple, and saying that's being "in sync" just tells me the author is single.
Showing basic skills of following instructions count as being used to cooking now?
I'm getting the distinct impression that there's a lot cut out from the novel. So many minor details that are interpreted as great signs of things they don't actually show.
She hit the mark.
Long hair is the best. Except for convenience. But it's pretty, so it's okay.