context: Rahul (Sharman Joshi) is one such young man with dreams. Working as a call center executive in a BPO in Mumbai. He silently loves Neha (Kangana Ranaut), A smart young woman who has made it up the ranks in a very short time. Hard work is not her only secret. She has done it only because her boss, Ranjeet loves her and is willing to shower her with gifts and opportunities, only if she is willing.In his 30s, Ranjeet (Kay Kay Menon) is married to Shikha (Shilpa Shetty) with a 6 year old daughter. Shikha is very well educated and was a better student than Ranjeet. She is also a talented dancer. They decided that she should stay back at home and take care of the house and the kid. So Ranjeet ventured out on his quest for money and success and forgot his family somewhere on the way. Bitterness and boredom crept into their relationship. Soon, he found solace and a fresh lease on life in Neha.Neglected by an indifferent husband and bogged down by family chores, Shikha is soon attracted to a maverick Akash. A loser and a rebel without a cause, Akash (Shiney Ahuja) is a struggling theatre artist whose wife divorces him because she cannot stand his failures anymore. Akash and Shikha's love blossoms and she almost crosses her limits that she has so fervently guarded all these years.Amol (Dharmendra) is a 70 year old man who's returned to India after 40 years to spend last few years of his life with his first love, Shivani (Nafisa Ali). This lady, who is Shikha's dance teacher, lives in an old age home and gives moral strength to Shikha.Shikha's sister and Neha's room-mate, Shruti (Konkona Sen Sharma) works in at Radio Mirchi. as a producer. She is a virgin at the age of 28 and is desperate to get married. She is dreamy eyed about her RJ, Wishy K. Her boss hooks her up with Wishy K. She also meets Monty (Irfan Khan) through a matrimonial site, but she is unimpressed by the straight-forward and socially inept Monty. When Monty stares at her, she is incensed. Monty however, likes her and is ready to marry her. Her affair with Wishy K blossoms.Rahul devises a novel strategy to step up the ladder of success. Most of the men in his office look for places to take their mistresses, girlfriends or prostitutes. He provides the perfect place to release their libido. His apartment. The cost? A recommendation for his out of turn promotion. Even Ranjeet gets the key and takes Neha to the apartment.Amidst one of their escapades Neha asks Ranjeet about their future. A commitment? Ranjeet makes it clear that she should not even think of a commitment. He insults her and leaves. She tries to commit suicide. Rahul discovers her in his apartment and takes care of her. They share some loving moments, come closer but still she's unsure about him.Shruti discovers that Wishy K is gay. She leaves the job and joins a new job where she meets Monty. Slowly, she sees the warm and caring person that Monty is and falls in love with him. She proposes to Monty at his wedding. Meanwhile the cat is let out of the bag when Shruti comes to know about Ranjeet and Neha. Ranjeet panics and confessed to Shikha about his relationship with Neha. An already guilt-stricken Shikha cannot hold it in any longer and tells him about her affair with Akash. Ironically, Ranjeet is shocked and angry, and decides to leave his wife. Shivani dies. Amol regrets the decision to leave Shivani 40 years back, stressing the importance of love to Shikha and Shruti. Meanwhile Akash decides to leave the country and invites Shikha to join him. On the other hand, Rahul is disillusioned with the way the metro has treated him and takes the bold step of resigning and decides to leave town. Neha realizes that Rahul really loves her, and chases him to the station. When Neha leaves Ranjeet, he immediately switches tracks and returns to Shikha, who is just about to leave for the station to see Akash.Neha chases Rahul. Monty chases Shruti. Shikha comes to the station but evidently not to accompany him. She wishes Akash good luck, tells him that she will miss him, and goes back home, back to Ranjeet. They all meet or cross each other at the railway station. And go ahead on their own paths. With lives they wanted. Or whatever the metro had destined for them.While the credits roll, we are shown that Akash still roams the streets of Mumbai, probably looking for a job. Shikha sees him and seems to have feelings for him, but has chosen her daughter's happiness over her own. Amol is leading the remainder of his life missing Shivani, but he realizes that he will always have the sweet moments that he and Shivani had togehter. Rahul has finally fulfilled his father's dream of owning a restaurant and is living happily with Neha. Shruti and Monty are happily married and have a kid- Monty's eye still wanders but Shruti has learnt to take it it in her stride
question: Who regrets the decision to leave Shivani 40 years back?
answer: Amol