Ash and N: A Clash of Ideals! (Japanese: 白の遺跡！サトシ対Ｎ！！The White Ruins! Satoshi VS N!!) is the 120th episode of the Best Wishes series, and the 777th episode of the Pokémon anime. It first aired in Japan on April 4, 2013 and in the United States on July 6, 2013.
Outside Dragonspiral Tower, Ash, Cilan, and Iris meet Professor Cedric Juniper’s assistant Nick, who offers them a ride to meet the professor at the White Ruins. En route, he tells them the excavation team may have made a fantastic discovery, but won’t say any more.
Inside the ruins, our heroes are reunited with Cedric, who shows them a door covered in mysterious symbols. He moves a few panels around, and the door comes open! There, in front of their awestruck eyes, is the Light Stone—an item straight out of legend that is said to be Reshiram in a different form! The professor picks up the stone, and it bursts into flame in his hands, sending a bright blast of light straight up into the air and leaving him unharmed.
From a distance, N sees the light and senses Reshiram’s presence. He makes his way to the ruins, surprising Professor Juniper and the others, and demands to know what the professor plans to do with the stone. Cedric explains that the Light Stone and Reshiram are part of his life’s work, and says he plans to investigate the stone thoroughly. N finds this unacceptable and leaps into action, grabbing the case with the stone in it and running away. Ash chases after him, but the ground gives way under his feet. N goes back to help him—even dropping the case to grab Ash’s hand—but finds himself falling as well, and the two of them land on soft sand deep underground.
Back on the surface, the others are trying to figure out how to get Ash and N out when they get some unexpected visitors: Team Plasma! The villains also saw the blast of light from the stone and followed it to the ruins, planning to get their hands on both N and the Light Stone. They’re prepared to attack Iris, Cilan, and Cedric when Nick reveals his true identity: it’s Looker, from the International Police! He corners Team Plasma’s Aldith and says reinforcements are on their way, but Colress activates his now perfected machine and takes control of the Golurk who have been helping with the excavation, turning them against our heroes!
Jessie, James, and Meowth have tracked Team Plasma to the site, but they decide to sit back and wait for the dust to settle before leaping in to steal the Light Stone and Pikachu. Underground, N and Ash are having an intense conversation about the relationships between people and Pokémon. N still thinks Pokémon would be better off without people, but Ash insists that he just wants to learn more about Pokémon and be really good friends with them—including Reshiram!
Then the two hear the sounds of battle above them and decide they have to find a way out. Who will claim the Light Stone when this battle is over?
Cedric Juniper and three of his assistants discover a chamber in the White Ruins with a strange puzzle on the wall that may hold the secret of finding the Light Stone. Meanwhile, as Ash, Iris, and Cilan are admiring Dragonspiral Tower, another of Professor Juniper's assistants drives up and takes them to the Ruins to meet with the professor, followed by several Team Plasma members. In addition, Team Rocket is watching from a distance and plotting their own ways of getting their hands on the Light Stone.
Upon arrival at the ruins, they marvel at the Timburr, Conkeldurr, and Golurk that are helping out the site workers, and then they go into the chamber to greet the professor. Professor Juniper explains how he believes there is something of great importance relating to Reshiram behind the door. Carefully sliding the different blocks on the door into different positions, the professor manages to break the seal and discover the Light Stone in an enormous, almost spherical chamber. Professor Juniper grabs the stone, which immediately engulfs itself in flames and shoots a pillar of fire out of the ceiling of the room – which is in a dormant volcano – and breaks through the clouds, which is noticed by both N and Team Plasma, both of whom immediately begin to head for the area where the fire came from.
As Team Plasma confirms the authenticity of the Light Stone and notifies Aldith and Ghetsis, Professor Juniper relates a story from the "White chapter" of Pokémon mythology to Ash and his friends. It tells of a special relationship between Reshiram and someone it deems to be a "hero", but goes on to explain how the hero's pure heart will be lost in the riches he will gain. At this point, N arrives and concludes the tale, startling everyone there. Hearing Professor Juniper's plans to analyze the Light Stone as nothing more than a scientific oddity and not a living being, N seizes the stone and sprints away, followed by Ash. Shouting to N that he wants to keep discussing the issue, Ash falls halfway into a pit hidden in the ground and N runs back to help him. However, N falls in as well, and the ground collapses entirely. In order to prevent Ash from falling, N drops the Light Stone down into the hole and grabs Ash's hand while holding onto the ledge, but his grip does not hold for very long and both of them fall down into the whole as well, while Cilan and Iris watch in horror. Although Iris tries to go down herself, Cilan and Professor Juniper quickly shout her down.
Ash wakes up on a mound of sand, with Pikachu standing there beside him. N soon approaches and verifies that Ash is all right, and indicates the Light Stone on top of the mound of sand. Unfortunately, the hole that they fell through is blocked off by very heavy rocks, and there is no other passage out, effectively trapping them. Meanwhile, on the surface, Team Plasma launches its attack on the White Ruins and surrounds Cilan, Iris, and the professor, as well as the other workers at the site, just as Aldith and Colress arrive. With nothing else to do, Ash and N talk about the relationship between Pokémon and people. N expresses his desire for Anthea and Concordia to see what he has seen - people who treat Pokémon as family, people who work alongside Pokémon, and people like Ash, whom Pokémon love being around - so that they can see some of the good in the world. However, Ash quickly rejects N's assertion that considering the Light Stone to be a "scientific interest" proves the arrogance and supposed superiority of people. He explains that he wants to become better friends with all Pokémon, and that scientists like Professor Juniper are using their findings to help better the relationships between people and Pokémon.
As Ash and N have this discussion, the situation steadily gets worse on the surface. Left with little choice, the assistant that brought Ash and company to the White Ruins accosts Aldith and reveals himself to be Looker in disguise. Using Aldith as his captive, Looker leads Cilan, Iris, and Professor Juniper away from the scene. However, Aldith scorns his actions as Colress uses his Pokémon Control Device to take control of every Pokémon in the vicinity, allowing Barret to rescue Aldith. Cilan and Iris send out Crustle and Dragonite to fight against the controlled Pokémon, but the fight begins to take a very bad turn as the sheer number of opposing Pokémon takes its toll. Team Rocket is watching the spectacle from the sidelines, preparing to claim the Light Stone for themselves once Team Plasma manages to find it. Suddenly, N reacts to the Pokémon's cries and informs Ash of the situation, to which Ash responds that they need to find a means of escape as soon as possible.