It's hard to give an exact time as it depends on the manga's plot development. But typically, Yuta Okkotsu shows up when certain events and character arcs lead to his introduction.
Well, it could be that in this fanfic, Naruto has developed a new jutsu that allows him to analyze and then replicate the DNA - like aspects of bloodlines. He might be using his vast chakra reserves to fuel this ability. For example, if he encounters a bloodline with a special element - like the Ice Release of the Yuki clan - he could break down the chakra signature and recreate it within himself.