Author: Amanda Wells
Source: Noise In My Brain
Kaworu Nagisa, one of my favorite EVA characters, turned out to be surprisingly popular on the Internet, despite only appearing in one episode. Curious being that I am, I tried to find a reason. Unfortunately, most Kaworu websites had since died (a consequence of getting into EVA years after its North American release), and those left didn't offer much of a glimpse into a Kaworu fan's mind. When I posed the question on AnimeNation's EVA forum, I mostly got variations on "he's cute". So I decided to pick the brains of the Kaworu fan I knew best: me. This resulted.
Among a cast of tormented, disturbed, and two-faced individuals, Kaworu--sweet, kind, and unflappably calm--seems to be the only character that's blatantly "lovable" in a classic way. That alone is enough to make Kaworu memorable, to capture attention of those seeking a respite from the anguish and chaos of later Evangelion.
Shortly after meeting Shijnji, Kaworu pinpointed his fears and problems, yet passed no judgement, positive or negative, on Shinji's (ignoble) coping mechanisms. While Shinji deserved a wake-up call more than a perfect friend, there's no denying the appeal of someone like Kaworu...to just about anyone. Many fear being judged by others, but also want to be understood by them. This doesn't just apply to broken individuals, but probably almost everyone who's not overly cynical and has some concern for their self-worth.
Kaworu's difference from the other characters and his "ideal" personality are the main reasons for his popularity, but there are others. Perhaps Kaworu has such a large number of female fans because many find that "nonthreatening pretty boy" archetype so attractive (of course, all female Kaworu fans can't be fangirls; I'm not). Kaworu is also mysterious, and some find mystery exciting. Perhaps some Kaworu fans like exploring his mostly-unexplained thoughts and motivations to create their own view of who he is. This contributes to Kaworu's popularity, because fans can "personalize" the character.
Mysterious, lovable, and an ideal, Kaworu is almost equivalent to the main characters in popularity.