I only visited Tsukiji late night.  There was something about being there when few others were that made me love it more.  It could have everything to do with my childhood in the Farmer's Market and understanding the "set-up" and preparation for the frenzy of customers that descend upon the stand.  Markets are always the most intimate to me before and after hours.  It is personal at those times.  Deep stories of hard work and family.  When the customers show up, it's about the service.  At times it is personal with repeat customers, but mostly, this is the show that goes on.  Truth, solitude and reality are darkest and brightest before and after the market opens.