I had a wall of text written speaking to my reactions to this Kids on the Slope, but in hindsight, it really was just an excuse to get people to watch and listen to the following.  So I'll save that for a later time and keep this brief.  Kids on the Slope sets up musical pieces as important points in its story: music that symbolizes the wishes and motivations of the characters.  In this scene, we see Kaoru and Sentaro, two friends and musical partners, coming back together to reclaim both their personal connections as well as musical connections they had lost.  Moving through My Favorite Things, Some Day My Prince Will Come, and Moanin', all pieces that set up major points in the story told so far, they remind each other as well as the viewers of just what they are reclaiming.
 
More, than anything else though, it just sounds so good.  So listen, and smile.