I think that, while slice of life, by and large, is more likely to provide more realistic Japanese than, say, mecha, space opera, hard battle, oni or vampire, steam-punk samurai, etc., any media product has to be understood to be artistically filtered. Characters and situations will likely be archetypal or obsessive and melodramatic,and the language will reflect such stylisms. It's best to seek out a wide range of media: web news reports (often with text of the audio), movies, anime, talk-show interviews (though these tend to be very rapid-fire), anything to get the widest exposure possible, and develop a sense of context.
