>>528478192
In the Memory Lane version of Sunny's house, you can find a chair outside the piano room. When examined, it says that Sunny would sit in that chair and listen to Mari play. It's presented in an innocent way, but I like to look at it more tragically by reading far too into it.
Sunny was getting to spend less and less time with Mari over time. She would practice piano, and recently she had started taking extra classes which kept her from home for even longer. Not to mention studying for college. Sunny cherished each and every moment he got with her. I forget where, but I remember it being implied that part of why Sunny wanted to play violin again is so he could spend more time with Mari through music practice. So maybe before that happened, he'd spend time sitting in that chair. Patiently waiting for Mari to be finished with practice so he can spend time with her. Hoping maybe she'll be done after this song. Or the next. She's only a room over, yet sitting in the stairway all alone in that chair makes her feel so far away. He misses her.