Which story? And who is hiding?

Answer

is

I was trying to depict the story of Surya and Saranyu who are married. But after a while Saranyu finds him overbearing, and decides to leave him. She makes a copy of herself (Chaaya/shadow) to live with Surya, whilst she escapes to live the life of an earthly mare. Surya realises much later that he has been living with a copy. Meets his father-in-law, who happens to be Vishwakarma. He trims him down a bit, to make him less overbearing. And Surya eventually discovers Saranyu, and they happily live ever after.