The author's two novels adaptation been released with the male leads being the pitiful ones and the female leads falls first:

Hidden Love

When I Fly Towards You

As for the others with similarity with First Frost maybe:

Back to Seventeen (with time slip plot, kinda like living together)

Because of Meeting You (iirc it follows the similar pitiful FL, ML falls first plotline)

Best Choice Ever (but FL previously dating other male, living together checked)

As for some with both leads pitiful, maybe:

Destined to Meet You

Love in Time

My Sunshine

 rxra7:

can anyone recommend me cdramas with the same vibes as this drama? 

I think Speed and Love will have the same vibe [its still filming] - only the role is reversed, its the ML who will have it though.