In the sense of, what is painful for the character, It would have to be her memories of her youth. Specifically between the age of 13-14 where she was accepted into VOCALOID; having to say goodbye to friends and family, as her friends moved on quickly and her family’s goodbye sour and bitter.Remembering the death of her mother also physically brings her the worst pain of all, in which she feels as if her heart has collapsed out of place, collapsing and crying; feeling as if she was the one who caused the inevitable death.
Rin can’t visit her mothers grave because it’s in the backyard of her family home; it brings her pain by even coming near the place. So she never could say goodbye to her mother and couldn’t stay for the funeral because of the mental damage done to her as well, she still cries knowing that she can never “ see her” again in a sense.
She likes to take her bow off sometimes and put it on the heads of people she trusts/loves (in a friendship or love-love way). She likes to think of it as; her mother meeting her friends, cause her mother gave her the bow, and yeah she likes to think that her mother still is next to her with her treasured bow with her.