Bishoujo Mangekyou -Wasurenagusa to Eien no Shoujo-

The protagonist, Kanzaki Akihito, was once a cheerful boy. Only having grown up, he was now with heart problems; friends of old were friends no more; and more often than not, he was not seen attending school. His mind was darkened mostly by his childhood friend and first love Sawatari Shizuku, and the fact that she had been unreachable for a while now. He felt as if she had betrayed him. Gray days pass by, and once more Shizuku appears before Akihito... Again the story starts moving, and to a direction not one of them had expected... [Translated from The Official Website]