How does Sin City use voice overs to establish the tone of film noir?

The opening of Sin City uses language to immediately set the tone and scene of the film, indicating it's genre, and themes throughout the rest of the film.
The voice over is of an American man, with a masculine husky voice, narrating the scene before the audience in a first person monologue, giving a detailed description of what he is doing, and what he is thinking. These are already heavily saturated in Noir conventions, as usually the character that is first introduced to us, is a man, and we are given some insight into what he has done, what he is thinking, or what he is doing. This is a theme present in older Noir films such as Double Indemnity where the audience are immediately first introduced to a male character, giving a speech about a crime he has committed, and it is through this that the audience are first aware of the immoral nature and ominous tones present within the film.
As well as this, the most important way in which the voice over suggests that it belongs to that of the Noir genre, is through the language and actions of the character. The audience are informed of the sophistication and the males seemingly high intellectual abilities through his well spoken voice, and immaculate grammar, that he is a man belonging to that of a higher class, which is again a common theme of the Noir genre, as it usually features the corruption and criminality within the upper class.
The opening Protagonist uses lines such as "I've been watching you for days" which the audience are aware has an ambiguous underlying tone, that he could simply mean he has taken an interest in her and noticed her recently, or that he has actively been watching her, but she is drawn in by his charm and deceivingly good looks, and as a result killed. This man takes on the features of the femme fatale almost in this clip, using his charm and physical appearance to lure her into a false sense of security, so that she is unaware to the dangers of being in his presence.  
By the use of voice over, it also shows the complex and developed character roles so commonly used within the Noir genre, for example, once engaging in conversation with the woman in a striking red dress, and seeing her vulnerability, he appears a gentleman, offering her cigarettes and an embrace, and then goes greatly in detail describing the woman in a fond manner, using lines such as "Her perfume is sweet promise that she brings tears to my eyes" which gives the audience the impression that he is greatly fond, and infatuated with her, and therefore happy to see the characters passionately involved, and whilst doing so, he kills her. This makes the audience ponder over whether he is an assassin who has a 'kind' way of killing his clients, or if he is simply a twisted man who likes to bring others false hope  before crushing any chance of them having a better life, either way, it certainly reflects the idea of moral ambiguity within characters from the opening sequence.
This event of the killing immediately sends the audience into a sense of confusion, and alarm, realising that they too had fallen for the typical narrative set up that we are so used to seeing in the mainstream box office, such as as the helpless beautiful woman being 'saved' by a masculine heroic man. By doing so, it makes the audience question all of the characters and events they see, speculating their true purpose and cause, setting the feeling of distrust and suspicion up from the beginning, as well as a more complex and real narrative, again all key traits within the Noir genre.