I don't have any OST that made me cry, but if its okay, I'll post an AMV of Nostalgia. The song is A Thousand Years द्वारा Christina Perri. This song really सूट्स their story. I cried so hard I was sobbing for the अगला couple of hours. ^^
XD Its because This ऐनीमे is from the same लेखक of Junjou Romantica, so art is quite alike. This ऐनीमे is Sekai Ichi Hatsukoi, its as amazing as Junjou Romantica! Do watch it! ^^