The film revolves around a nameless protagonist, often referred to as "Naanu" (Me), who represents the raw, unfiltered human ego. Unlike traditional heroes, Upendra’s character is unapologetically selfish, driven by his own desires and a disdain for social pretenses. The story is told through a non-linear narrative, weaving together his complex relationships with three different women—Rathi, Keerthi, and Swathi—each symbolizing different facets of human emotion and attachment.

What made Upendra a sensation in 1999, and why it remains relevant today, is its philosophical depth. It wasn't just a movie; it was a mirror held up to the audience. The "Naanu" philosophy suggests that every individual is the center of their own universe, and altruism is often just a mask for self-interest. This radical take was unheard of in the late 90s, especially in the South Indian film industry, which was then dominated by formulaic family dramas and action films.

The technical brilliance of the film also deserves mention. With its rapid-fire editing, experimental camera angles, and a hauntingly unique background score by Gurukiran, the movie creates an unsettling yet addictive atmosphere. The dialogues, sharp and satirical, became instant catchphrases, sparking debates on morality and spirituality.