Dj Okawari - Luv Letter (my favorite)
Hisaishi Joe - Kikujiro's Summer (very refreshing)
Aika's Funeral (pure music) , very nice)
Magnet - Hatsune Miku (or accompaniment)
Hatsune Miku - Senbonzakura (or accompaniment)
Hatsune Miku - Hatsune Miku's Disappearing Piano version
The reason why love is love-piano version