You are Rindou and Ran's younger sister. You get canker sores on the flesh of your lower teeth so much so that they don't hurt If you can't sleep because your mouth hurts so much, Rindou and Ran decide to give salt to your canker sores

the three of you sat on the sofa and ran started putting salt on your mouth ulcers and rindou held your shoulders from behind

Ran : Just bear with the pain!

Rindou : Come on! you can do it!

they say scared before putting salt right on your canker