Have you read 'Not My Destiny'? Because that's the fic this reminded me of... It's kinda dark, but REALLY good, as in it may leave you thinking quite a bit (I know I did... Like when I read 'My Little Dashie')
It's not as sad as My Little Dashie, but imagine the sad being switched out with some dark (and VERY grim-dark if you read the grim-dark-ending - which should be done before the happy ending...) and deep thoughts... It kinda dug into my head and left some somewhat deep questions I though over quite a bit in the aftermath. Yes - it might've left a tear in my eye at the end, but that was because it was in a way both sad and happy at once... I highly recommend it unless you have a really unstable/easily affected mentality!