The visible tree belongs to the present environment, but the root belongs to the birth. Here the story swings around this concept.
We never forget day to day events but suppress them under our conscious mind. Just a clue or smell is enough to bring to our attention.
What we need is a clue, it can trigger our emotions.
Here assume invisible Karthick as an event happening around Arvind Swamy. Suppose Arvind comes to a function and never met karthick also, Arvind would have gone through the same experience but a different one. Arvind is angry with the society that kicked him out of his home. He never wanted to come because some events discarded him from the root.
Karthich is nothing but a shadow of events to trigger his nostalgic moment. He is an alien or may be a representative of GOD not a human, that’s why he is foolproof and unique. Karthick was never there but an invisible force that made Aravind to connect nostalgic events.
(Note : Karthick represents God that’s why he was able to live with snakes like in EDEN, where god lives with serpents. Aravind is an Adam who returns to EDEN with a hate towards GOD (karthick), later he understands him and goes back to him in the climax. Even GOD (Karthick) forgives ADAM (Arvind) and helps in terms of money to buy the existing house.)
Lovely movie!