Pain (2011)

Both male leads are willing to get hurt or die in order to protect and save the female lead.
Both have female leads that can be cured but that causes more problem for the male leads.
Both are sweet, sad and romantic.

Both movies show a raw beauty of a growing relationship between a man and a woman that have many differences but still fit somehow fit perfectly with each-other.

The whole story structure are much similar. Both struggling main lead, heroine is trying to live in the right way and the hero is doing the brute work and getting used by others. Meet , help and fall in love. There's no mention of age gap though.

In both movies I could see lot of similarities such as both movies deal with bittersweet love story. Male lead trying to protect Female lead.Female lead is homeless.Male Lead and Female Lead staying at same place.Male lead involved in illegal activites