Madhu wants to keep a fast for KC. No surprises there. When she did it for RK the previous year even when their relationship as husband and wife had not concretised, now that they are officially husband and wife and have become one with each other in body, mind and soul, the ritual only assumes that much more significance for her.
RK never believed in KC and was adamant that she does not hold it even in the previous year. However, he did indeed break her fast when he realised how stubborn she was. This time around he wanted to show her that he was equally, if not more stubborn than her and was not going to let her have her way.
Let us take a step back and see the backdrop against which this whole ritual was done. Madhu had been told by Pabho that the Guruji had told her that Madhu spells ill omen to RK and he will be destroyed by her.. Observance of all the rituals associated with KC would have therefore been more important for her because she would like do everything within her power to ensure RK's long life. Madhu's role as a wife was paramount to her.
RK, on the other hand, has different considerations. Madhu has made things difficult for him because of her zealous observance of the wifey role exhibited in her penance and poojas or her inhibitions about shootin certain scenes. His director has threatened to walk out on the film. They were running behind schedule and if Madhu does not alter her ways, they could be facing financial ruin. So he took it on himself to get her out of her wifey role and immerse her completely in her heroine character and picked the KC for doing it, knowing how staunchly attached to this festival she is. Madhu's role as his heroine was paramount to him.
What RK failed to understand or acknowledge is that Madhu was capable of discharging both roles effectively if given half the chance. She would have fulfilled all the poojas and penances Pabho wanted her to do and still have made it to the shoot in time to give her best if Dips and Pabho did not play dirty. She could have observed the fast and still given the shots perfectly had RK gone as per the original schedule and not forced her to do a dining scene or thrust a double shift not only on her but the rest of the crew.
Having said that, Madhu too should have acted more sensibly and sensitively to address her husband's concerns. If she had spoken more calmly and reasoned out with RK instead of pouting and throwing him looks of daggers, maybe things could have turned differently. RK did feel bad by the end of the day and had come to apologise to her.
Anyway let us take our leads for who they are - pig headed, stubborn and dogmatic in their own ways and look at whether they stayed in character during this particular track. I think that, by and large, they did stay within the contours of their characters with all their flaws. Madhu will bear anything for her RK's sake, even if it means fighting with him or facing humiliation from him. Right now RK's life is her priority and she will not endanger it because of failure to follow some ritual which could ensure his longevity. She could have told him that she did not break the fast because of the scene but then she did not care to explain herself to a man who would not stop at humiliating her in public. He can think the worst of her if he wants to but she will finish what she set out to.
RK, on the other hand, seems to be irrational and ruthless but this has been his biggest flaw. The guy has a king sized ego which has lately been battered by all and sundry. Madhu has in her own way contributed to this, although unintentionally. So he is like a horse with blinkers. All he can see now is getting his film completed successfully and he will do whatever it takes to achieve it and shut all his detractors. If he found Madhu's actions unprofessional, he will speak his mind, no matter the people around or the place. This is the man who performed the unwedding. This is the man who linked her up with Sultan and that too in a public party. Was he not in love with her when these things happened? He was very much in love with her and yet he tore her to pieces when his pride and ego were hurt. He may have realised his follies and mellowed down considerably since then but his basic traits lie just beneath the surface and emerge at the first provocation.
Another point to be noted in RK's character is that he is very vindictive by nature and assumes that others are as vindictive as him. So when he told Madhu that he knew she was getting back at him by changing the fast breaking scene as a tit for tat for his unscheduled dining scene, he really believed she would do that because that is what he may have done if he was being arm twisted into doing something he did not want to do.
So both of them were wrong in what they did and how they went about handling the situation but then were they out of character? I think not.
Finally what was achieved in all this? Whether Madhu realised it or not, she is really turning out to be a great actress. She managed to fool the smart and shrewd RK, not once but twice in the two scenes in which she figured. RK had set up the scene to prematurely break her fast. He thought that the reel eating had turned to real eating but Madhu retained 'reel'ness of the scene. She sold him a dream without making it a reality. In the next scene RK was under the impression that he wasn't really breaking her fast since it was already broken in the previous scene but Madhu this time turned a reel scene into a real scene but actually having her fast broken by the man who swore he wouldn't break it for her. RK may have told her that she was unable to break from her s role as his wife but the day's events showed that she was equally successful in her role as the heroine.
The reason why she would be successful as an actress is because she is doing it as a wife who is keen to help her husband. In other words, it is because she thinks as a wife, she is able to be the actress he wants her to be. I hope RK realises this at some point.