Nano makes his first appearance in the first episode, during the intro to the series. In the anime (and manga), Nano is often shown lurking on rooftops as a passive observer of the story's events.  He leaves vials of Line for the people of Toshima to find, and tosses one directly to Takeru in Episode 5. As most people use Line in order to enhance their abilities, Nano seems appalled by human nature. Later on, in episode 7, he encounters Akira. After a few stoic words, he instructs Akira to give this case (that is filled with enhanced Line) to a man who will come soon. Akira asks him who he is in confusion, but Nano answers Akira's question with a riddle and walks away. When Shiki arrives to take the case, he tells Akira that the man who gave it to him is "Fear".  

Anime Nano

Nano as he appears in the Anime, Ep 7.

In episode 10, it is finally made clear who Nicole Premier is. After saving Akira from Gunji, Nano teleports an unconscious Akira and Keisuke to a secluded safehouse. Moments later, Emma and Gwen arrive and put both Akira and Nano at gunpoint. It is then explained that Akira was a part of Project Nicole, a genetic engineering program to create a drug which enhances the natural capabilities of humans. Emma tells him that his blood is the antidote for said drug, and is the reason he was framed for murder and placed in Igura: Emma wanted to use him to lure Nano out, whose blood is the source of said drug. 

In the 11th episode, Nicole Premier is confronted by Shiki. After a staredown, it is revealed that the two have met in the past during the Third Division and that Shiki was purposely spared during a bloody fight between Nicole Premier the super-soldier and Shiki's military unit, which no one else survived. When asked why he was spared, Nano tells Shiki that he spared him because he wanted to experience the feeling of dread that was born within him that day; he would surely come back to him in the future. After a long fight between the two, Nano realizes that Shiki is only motivated by gaining absolute power in order to eliminate that feeling that was put inside him that day and offers Shiki his pure blood, that would make him as powerful as him. Without second thought, Shiki lunges at Nano and sinks his teeth in neck, drinking his 100% pure Line blood. Miraculously, Shiki survives this and gains insurmountable power as a result, even surpassing Nano and managing to injure him.

In the series finale, Nano yet again fights Shiki, who is now able to best him in combat. Nano next appears before Akira and Rin and helps them escape Toshima. This is the last time Nano appears, as he heads towards a unit of soldiers who are shooting at him and easily butchers them. He is presumed to be alive and still dwelling somewhere in Toshima.