A sudden kiss
She is lucky there is somebody who is looking out for her so much. When Mamoru died, their mutual friends did their best to help her out. But everybody was in pain too. They could not focus their attention on her when they are grieving as well. She cannot expect anybody else to understand the pain she is going through. Atsuro was the only other person who knew Mamoru was sick, but she could not rely on him due to what happened. She was backed into a corner and did not know what to do.
For so long, she was in pain and could not breathe. She spent many days in agony, with pain in her chest. It hurts, it hurts so much.
Ever since she came to Tokyo, Sumire realized she could breathe again. She no longer felt suffocated. The main reason for that is undoubtedly this person who is beside her.