N in the Black & White chapter
N first appears in Black's First Trainer Battle, where he watches Black set off to battle his first Gym. In Lights, Camera...Action!, N witness Black save a Xtransceiver commercial shooting from a wild Galvantula attack. Once the ordeal ends, N sheds tears from seeing Pokémon being used by humans.
In Letting Go, N confronts Black at Accumula Town to battle him. During the battle, N expresses his disgust at the Pokédex by claiming that Trainers lock up his "friends" in Poké Balls to fill the Pokédex with information, thus making them nothing more than a source for said information. After a tough battle, Black's Tep manages to defeat N's Tympole, which shows N that there are some Pokémon that enjoy the company of their Trainers. After N leaves, Black sees a dream from N's past that his Musha ate and produced with its Dream Mist. Seeing a young N surrounded by Pokémon makes Black wonder if N isn't truly a bad person.
In Gigi's Choice, N traps White on the Rondez-View Ferris Wheel in order to talk with her. After finishing their conversation, N talks to White's Gigi and asks if wants to battle like Black's Tepig did. N has his Servine grab Gigi, which forces it to knock Servine out with an Ember. White, shocked at Gigi's joy at battling, chooses to open the car door and jump out. White tells Gigi to come with her, but falls out of the car after seeing Gigi choose to join N instead. As White lies on the ground unconscious, N reveals that he intends on defeating the League Champion. Afterward, he sends Servine down to assist White.
In Finding Truth, N receives the Dark Stone from Ghetsis. With it, he successfully awakens Zekrom, the Legendary Dragon Pokémon of Ideals. After some initial struggles, N successfully convinces Zekrom to join his cause, thus becoming the Hero of Ideals. In The Lesson Ends Here, N encounters Alder at Route 6 and challenges the Champion to a Double Battle. After a long battle, Alder is defeated by N, which Black, White, and Iris arrive in time to see. Reacting to Zekrom's presence, the Light Stone in Black's possession turns into Reshiram, but quickly reverts back into stone form, signifying that Black doesn't have full control over it. Having emerged victorious over the Pokémon League Champion, N claims that more people will begin to listen to Team Plasma's ideals.
As he attempts to leave, N is attacked by a Samurott owned by Cedric Juniper who demands to know where the Gym Leaders that were captured by Team Plasma are being held. Together, Black, White, and Cedric manage to defeat N's Pokémon. Cedric reveals that a year ago, N broke into his lab and liberated a set of starter Pokémon that he was going to give to new Trainers. The Snivy stayed with N, the Tepig ran out in the rain, while Oshawott chose to stay with Cedric. N accuses Cedric as Professor Juniper as the cause of the suffering of Pokémon with their distributing of starters.
Trying to figure out a way to stop N, Black attempts to use Musha to clear his head and allow him to think properly, but the Dream Eater Pokémon simply runs away. N reveals that Musha doesn't like the taste of Black's dreams anymore, so he has no reason to stay at Black's side anymore. The shock of his Pokémon leaving him causes Black to faint. After reviving his Pokémon, N leaves on Zekrom while Zorua and Tympole destroy the third Unova Pokédex. As he flies away, N hears Zekrom's voice and learns that it wants to battle Black again when Reshiram has fully awakened.
In Cold Hard Truth, Team Plasma begins their attack on the Pokémon League by summoning N's Castle from the depths of the earth. N, along with the Seven Sages, begin their assault as the Grunts surround the people below. Black, having awakened Reshiram, battles N at the top of the castle. Black initially has trouble fighting with Reshiram, but gets help from Cedric Juniper to better learn Reshiram's types and Abilities. By exploiting the power of Fusion Flare, Black deals heavy damage to Zekrom, but it and N escape to inside the castle with Black and Reshiram following after. Once inside, the two continue their battle, but a second Zekrom appears to assist the first, much to the shock of both.
Black sees through the ruse and attacks the real Zekrom, defeating it. The second Zekrom reveals itself to be Zorua, who had remained to help N despite him releasing all of his friends prior to the attack on the League. Black tells N that despite the release, Zorua truly cares for N and wants to stay with him. N thanks Zorua, but scolds it for its actions just before passing out. After Black defeats Ghetsis and meets up with White, N awakens. He thanks Black and White for helping him see the error of his ways. He decides to go on his own path and bids them farewell as he leaves on Zekrom's back, leaving Zorua behind.
In Flying Ship, N and Zekrom flew towards Unova, Zekrom having been attracted to Kyurem's growing power. As they traveled, the Light Stone arrived and flew with them before stopping at the Entralink. At the Entralink, N reunited with White after she obtained the Light Stone. N and Zekrom took White to the Plasma Frigate, Team Plasma's flying ship. N revealed that Kyurem had attracted Zekrom and Reshiram to it so it could fuse with either of them. Shortly after arriving, Ghetsis exited the Plasma Frigate and used Kyurem to battle with his former son. As they battled, N had White move to safety and told her that if Zekrom were to be absorbed, the Light Stone would react to Kyurem's power and revert back to Reshiram.
In PS543, Ghetsis obtained the DNA Splicers, which gave Kyurem the power to revert Zekrom back into the Dark Stone, sealing N inside with it. N ended up at the Pokémon Dream World, where he reunited with Black. Reacting to Zekrom being sealed, the Light Stone pulled White inside of the Pokémon Dream World as well. After Kyurem absorbed Zekrom to become Black Kyurem, Black told N to stay behind and fight Kyurem from the inside while he and White exited the Light Stone with Reshiram to fight from the outside. After exiting the Light Stone, Black and White launched a combination attack against Kyurem, but stopped after noticing N was ejected from the Dark Stone. Not wanting N to interfere with Kyurem's fusion with his abilities, Ghetsis knocked N off of Kyurem's back, sending him to the ocean below. In PS546, it's revealed that N was picked up by Colress before he could hit the ocean, and is seen unconscious and chained to a table on the Plasma Frigate.