Protagonist falls in love, The woman is killed tragically. Greif stricken the man attempts suicide in doing so he's transported to a physical realm of his own memories that become more evil the longer he is there. He must fight the physical manifestations of the sadness of losing the love of his life and suicide to escape the treacherous domain.

Suggest something like:

When his girlfriend tragically dies a young man unsuccessfully attempts suicide, only to find himself plunged into a nightmare world between life and death, of which he now must escape.