Sumod : Stolen Smile

" You have stole her smile Agni " said a broken pramod having tears in his eyes .

" I am sorry pramod bro mein mummy ki Kasam se bandha hua tha " said a guilty agni .

" Don't call me your bro you know what voh uss din se hasna bhul gayi hai you and your mother have destroy everything . She never smiled wholeheartedly after that day . " said pramod in her care .

Who is she ?
About whom pramod is talking to Agni ?
What has happened to her ?
What happened that day ?
What was that Kasam given by Agni's mom to Agni ?