The story commences in the suburbs of Chennai at a retired military officer, Thanikasalam's house. Theirs is a well off family consisting of Thanikasalam, his wife Rajeshwari (Raji), his eldest daughter Gayathri and the youngest daughter Suja. Having completed her MA, Gayathri dreams of doing MPhill and becoming a lecturer. Yet her parents wish to see her settled down. One fine day, as Thanikasalam walks along the roadside with a pot of Goldwish, two motorist bypass him in full speed, making him startle and drop the pot. An angered Thanikasalam finds out the boys are none other than a well know Rice Mill owner , Annamalai's nephew Mugundhan and son. He decides to go see them. In the meantime, Mugundhan and Krishnan (Annamalai's son) are elated at seeing the government job order for Mugundhan. As they zoom away, they do not realize that they hae knocked over Thanikasalam's fish pot, hence do not stop. Thanikasalam, at Annamalai's house is welcomed by the members of the latter's family. He is not given a moment to explain the purpose of his visit. A few moments later, Mugundhan and Krishnan walk in and share the great news, distributing sweets. Thanikasalam's anger melts down seeing the happy nature and the unity of this joint family, and soon he walks away without bidding bye. Back at his residence, he shares this accidental meeting of such a wonderful family with his family, further adding that he wishes to see his eldest daughter in that household. This sparks an argument between Gayathri and Raji, leaving a few hearts to break.
At Annamalai household, Mugundhan is seen depressed and his immediate family members eventually get to know the reason for it - Mugundhan isn't keen on going far away from his family members to attend this job offer, however, when he tried to get a transfer to the nearby branch, he was asked a lump some of 2 Lakhs. Since Annamalai had bared Mugundhan's education expenses, Ranjini (Mugundhan's sister) advices he goes to the original place of job offer, while Azhagesan (Mugundhan's father) and Senthil (Ranjini's husband) try to think of a way. However, Krishnan hears this and assures Mugundhan they can get the money from his father Annamalai. As suggested by Krishnan, Annamalai does offer to give money to Mugundhan, showering lots of love on him. What strikes everyone here is the ill treatment of Krishnan by Annamalai and the reason for it being Krishnan dropping out of school in 10th standard. In order to meet Mugundhan's need and due to tight financial circumstances, Annamalai is forced to withdraw the money they had saved under his wife Parvathy's name for her heart operation. Though Ranjini opposes at first, Annamalai tells her that the surplus from the Rice Mill would be in after 2 weeks. As such, Krishnan withdraws the money from the bank and hands over to Mugundhan to be submitted to the officer prior to leaving for work. On his way back home, Krishnan notices an absent minded Tanikasalam walking along the road, not noticing an opened man hole. Before Tanikasalam falls in, Krishnan saves him and takes him to his house. Both Krishnan and Thanikasalam recognize each other, and the latter and his family members are pleased with Krishnan's help. Mugundhan, on the other hand, while going to submit the money, gets robbed. Not knowing how to face Annamalai, he informs Krishnan and the latter takes the blame as well as saatai adhi from Annamalai. Though the mistake was his, Mugundhan doesn't come forth to tell the truth. Instead he accepts all of Parvathy's Jewelleries offered by Annamalai to play the fees.
In the meantime, after much thought Gayathri agrees to get married as per her parents' wish and Thanikasalam happily goes to fix the marriage alliance with Annamali. Not being able to meet Annamalai, Thanikasalam passes the message onto Azhagesan. Having eves dropped on this, a plan cooks up in Senthil's mind! He wishes to see his step sister, Chitra married to Mugundhan. Hence he suggests to Azhagesan that they get Krishnan married to Gayathri. After a brief discussion with Ranjini, Azhagesan passes on the message and Annamalai readily agrees. However unlike Senthil had planned, Annamalai wanted Gayathri to pair with Mugundhan and Chitra with Krishnan, considering their education backgrounds. With the horoscopes matching, the groom side wishes to go see the brides. However both grooms - Mugundhan and Krishnan feel shy to go see their respective to be wives. So the brothers with the elders permission decide to go see their to be sister in laws. At Thanikasalam's house, a smartly dressed Krishnan comes across as an intellect himself, as he wears a Bluetooth to find out the answers to Mugundhan's question. Gayathri too doesn't mind answering her to be brother in laws questions. Mugundhan on the other hand is bowled over by Chitra, and falls for her. This brings about the turning point in the story. He plots a series of events to prevent Krishnan from meeting Chitra. However to stop himself from getting married to Gayathri, and Krishnan from getting married to Chitra, he writes a letter to Thanihasalam damaging his own image. He also sends a letter to Chitra's house as well tarnishing Krishnan's image. Thanihasalam decides to give his daughter's hands to Krishnan, purely basing it on Krishnan's goodwill. As he approaches Annamalai, the latter is taken aback and blames Krishnan. A fight breaks out and Parvathy is hurt in the process. She is admitted at the hospital, immediately needing a bypass.
To fulfill Parvathy's wishes as well as at Mugundhan's kind request, Annamalai agrees to get Krishnan married to Gayathri, and Mugundhan to Chitran. The marriage takes place, and all are happy. The newly married couples share happy moments in the meantime. Ranjini all she can to prevent Gayathri from knowing the truth about Krishnan's education since she is afraid it'll blow Krishnan's marriage life away. However, on the day of the Shanthi muhurtham a week after their marriage, Gayathri gets to know the truth and she leaves to her parents' house. Krishnan is shattered. The same night Krishnan goes over to Thanikasalam's house to bring Gayathri back, however she is adamanat and accuses his family of cheating her. A furious Krishnan raises his hand to slap her, but is stopped by Thanikasalam, who asks Krishnan to leave. A shattered Krishnan returns to the MIll instead of his house, and spends the night their all alone. The rest of the family members find out about it the next day. Ranjini tries to pacify him and bring him home, but Krishnan refuses. Ranjini requests Annamali to go and console Krishnan, and he does.... however, even he isn't able to console Krishnan.
An angered Annamali goes to Thanikasalam's house to question them about Gayathri's actions... for which Thanikasalam shows the letter he got accusing Krishnan to have written this. Annamalai falls for this and goes directly to beat up Krishnan. Ranjini rushes to the scene and saves Krishnan. Mugundhan, in the mean time remains quiet and pretends to act all innocent. In addition, he blames Krishnan's fate for all the happenings and wishes to continue his happy married life with Chitra.A heartbroken Krishan wows to find out the real culprit behind the letter. Raji, in the mean time, tries to make her daughter understand how a woman should be post marriage, however, Gaya refuses to live with a man who is illiterate. One day Krishnan finds out the truth... that Mugunthan was the one who had written the letter. He is shattered and can't seem to understand why his own brother would do such a thing. Seeing Krishnan like this, Ranjini follows him and wants to know why he is upset. Krishnan brushes it off as nothing, however, is forced to tell the truth eventually. Ranjini is stunned, and is tongue tied by Krishnan. Annamali in the meantime continues to hold a grudge against Krishnan. All this while, everyone managed to hide the Krishnan - Gayu separation from Parvathy. However, as soon as she returns home, she gets to know it all. Eventually, Parvathy finds out the truth about the person behind the letter and fumes in anger. She tries to directly attack Mugunthan without letting the matter. Mugunthan is worried and goes to Senthil for advice. Senthil being a schemer advices Mugunthan to create more problems to divert everyone's mind. Hence, Mugunthan begins his first attack on Annamali. He confront Annamalai regarding the family properties and accuses Annamalai for having to treat his father and mother as slaves. Annamalai is heartbroken and decides to hand over the Rice Mill and house leadership to Mugunthan and Visaalam, respectively. He also hands over the pass book to the savings he had done under Azhagesan's name. Azhagesan and Visaalam are ashamed of their son. Mugunthan and Senthil consider this as their first victory.
Gayu's anger towards Annamalai family remained as it is, and she refused to listen to Raji's plea. She then decides to teach at a tutorial, and is surprised to see Krishnan there. She challenges to kick him out of school as well. In the meantime, Gowri and Suda try to make things between Gayu and Krishnan by bringing them under one restaurant. However, an unexpected event occurs.... as Krishnan tries to make Gayu understand, the latter slaps him. Krishnan fumes in anger and drags her to her house and locks both of them under closed doors. Not knowing what happened behind closed doors, Thanikasalam goes to fight with Annamalai and co, but later learns the truth from his wife and daughter Suda that Krishnan did nothing, but pour his heart out. Thanikasalam realizes his mistakes and has a better impression of his son in law now. Annamalai also gets to know the truth about the letter and makes up with his son Krishnan. At the same time, they all find out that Ranjini is pregnant. However on the same day, the falling of Lord Murugan's picture forces Annamalai to go see the family astrologist only to find out that the moment his daughter Ranjini gives birth to a baby, his life will be taken. He is shattered, however, keeps it a secret. Parvathy also undergoes a few events signifying bad omens, hence she also visits the astrologist and learns the truth. She too is heartbroken and tries to find ways to abort Ranjini's baby. The moment Annamalai finds out that Parvathy is trying to harm the unborn child, he warns her. However, she isn't able to digest this and leaks the secret to Ranjini. Ranjini is shattered and also wants to undergo a miscarriage. She consumes poison to abort the baby, but is saved. Annamalai gets her to promise that she'll no longer do anything to harm the baby. Ranjini, with no heart, promises. However, Annamali pours his heart out to Krishnan.
Gayathri continues to hold a grudge against Krishnan and even sends him to jail for something he never did... and doesn't realize that it is all a game played by Raja, one of her students. Krishnan is beaten badly and is hospitalized. An outraged Parvathy curses Gayathri, while Raji and Thanihasalam scold her. This event results in Gayu returning to Annamalai's house, not out of her own interest, but to get a divorce, eventually. Despite living in her in laws, Gayathri considers everyone in the house a stranger and ignores them. However, her friendliness towards Raja makes Annamali warn her. But Gayathri raises her voice against him, angering Krishnan. He gets hold of a belt and beats her up. Even though people tried to stop him, he doesn't listen and continues to beat her up. A furious Gayathri challenges Ranjini the next day and files a complaint against Annamalai, Azhagesan and Krishnan. The police too come and arrest them. All are shattered, while Gayathri continues to justify her acts. However, Raji gives her a piece of her mind and gets her to withdraw the complaint. Even after all this happens, Gayathri continues to stay at Annamalai's house and challenges them that she'll make the people of the house chase her out of the house forever. Raja continues to act innocent and traps her. One day he invites her over to his house to meet his ill sister. Gayathri also goes... but he pretends to be sick himself and gets Gayathri to help him. A bunch of his friends watch this from outside and assume something else. The next day the entire tutorial speaks badly of Gayathri. The higher heads also decide to fire Gayathri. The latter tries to prove her innocence by bringing Raja there, but he likes that he in fact did have an affair with her. Gayathri is shocked. At Annamalai's house, a marriage proposal has arrived for Gwori. The family visits the house. Just then Gayathri arrives... and one of the members, who also happened to work with Gayu, spills the beans about Gayathri's act with Raja. All are shocked and the family decide to leave this sambantham. A furious Parvathy shows the doors to Gayathri. A devastated Gayathri goes to her mom's place, only to be chased away. She has no place to go, hence, decides to commit suicide. But Krishnan saves her clears her name by bringing the truth out of Raja's mouth. However, Parvathy is not ready to accept Gaya.
While things continued to remain the same, Mugunthan and Senthil are suspicious over Annamalai's sudden withdrawal of 10 lakhs. They decide to follow him and realize that he is helping out a young girl (Devi), who happens to call Annamalai "Appa". They decide to bring this into lime light and call Devi over to Annamalai's house. As Devi calls Annamalai father, everyone are stunned. Annmalaai just tells them that she indeed is his daughter and leaves with her. Azhagesan follows him and asks Annamalai if what he is thinking is correct. Annamalai nods and leaves. Azhagesan is dejected and goes to the room to think of the past.
Annamalai (AM) and Azhagesan (AZ) are the only occupants of the house. AM's main goal in life was to make AZ a well educated man, hence he works hard to achieve his goal. AZ on the other hard isn't interested in studying, and wants to help his brother. But is going to college to fulfill AM's requests... however, he also falls in love with a girl. A friend of AM happens to see this and informs AM. The latter requests AZ to get married if he considers himself as his father. AZ doesn't object and marries the girl of AM's choice, Visaalam in 1979. Soon he sees his girl friend, Sarasu, one last time to inform that he had to go for the girl of his brother's choice, which he couldn't reject. Hence asks her to move on. Soon after, Visaalam and AZ have a baby girl... and the family are happy. However, in 1987, AZ comes across his ex-girlfriend Sarasu and learns that she is in hardship, i.e. that she lost everything when her mom fell ill. AZ is disheartened and meets her. An year later, Sarasu delivers a baby girl and dies. AM learns about this and takes the baby, Devi, from AZ and raises it himself.
When Annamali arrives home, Parvathy questions him and he tells that Devi is indeed his daughter. Parvathy decides to leave but Krishnan stops her and tells her the truth, his father had told him earlier. Parvathy feels bad and apologizes to Annamalai. However, the latter gets Parvathy not to let this matter out. She too promises. Devi, in the meantime, feels lonely and wishes to be with her father's family, however, when she goes to take a family picture, Mugunthan scolds her and sends her away.
When Annamali learns about this, he goes along with Azhagesan and tells Devi the truth and bring her back to their house. However, Muguthan doesn't like this idea and insults Annamali and Devi. Even though Azhagesan tries to reveal the truth, Annamali tongue ties him. Mugunthan raises the fact that if they have to accommodate Devi, then they'll have to split the family properties. Annamali is heartbroken. That is the last thing he wanted to do, hence he gives everything to Mugunthan and co., and leaves out of the house along with his family. Azhagesan runs after his brother to stay with him and not to go any where, but Annamalai says the time has come for them to split. Moments later, his words become true.... he suffers a heart attack... he gives all the responsibility to Krishnan and leaves everyone. Simultaneously, Ranjini gives birth to a baby boy. Gayathri also realizes her mistakes and come to apologize... but is shocked to see Annamali no more. With that the family splits.... Parvathy refuses to accept Gaya and also Azhagesan's plea to come back. She takes her kids and goes to the house Devi was living in.
To be continued as story progresses....