Ash and his friends, along with Sawyer, have arrived at Snowbelle City. Bonnie starts playing in the snow, despite Clemont's warnings that she'll catch a cold. Serena and Sawyer hope Ash will win his eighth Badge. Bonnie also hopes to see Ash-Greninja, the form when Greninja syncs with Ash, which Bonnie gave a new name to. Serena approves of the idea, even if Clemont thinks the name is a description. Before they arrive at the Gym, as Bonnie, Serena and Clemont speed up, Ash wishes to obtain the final badge and battle Sawyer in the Kalos League, as a rematch from the defeat Ash received. Sawyer approves, but are called by Serena to hurry up. Inside the Gym, Ash requests a Gym match. This causes a mechanism to trigger and reveal five Bergmite. The screen warns the heroes and Sawyer the interior is also very cold. The door opens, revealing a man, who congratulates them for managing to come here so far.
Ash requests a match from the Gym Leader, whose name is Wulfric. Bonnie wonders if it is cold to sit on ice. Wulfric laughs, thinking ice also has a warm heart, and the temperature suits him. Wulfric notices Sawyer, whom he battled the other day. Sawyer confirms this and thanks for the battle, which Wulfric claims it was "a heated one". Ash introduces himself and tells he has seven badges. Wulfric understands this is the battle for the final badge, one Ash should enjoy. Ash leaves his coat to Serena, ready to get fired up. At the battlefield, Wulfric claims ice can be hard and fragile, meaning his strategy will change, depending on which Pokémon Ash will send and which moves are used. Ash sends Hawlucha, who nearly slips down on the icy field, while Wulfric sends Abomasnow. Abomasnow's presence starts hail, due to its Snow Warning Ability.
Hawlucha starts off with Flying Press, landing a hit on Abomasnow. Wulfric recognizes Hawlucha has spirit, but Hawlucha takes damage from the hail. Hawlucha uses High Jump Kick, but gets hit by Abomasnow's Ice Shard. Abomasnow charges head-on with Wood Hammer, but Hawlucha evades the attack and knocks it down with Flying Press. Hawlucha uses High Jump Kick, circles around Abomasnow and hits it in the face, defeating it. For his next Pokémon, Wulfric sends Avalugg. Hawlucha dodges Avalugg's Stone Edge and hits it hard with Karate Chop. However, since it is hailing, Avalugg's Ice Body restores some of Avalugg's health. Hawlucha attacks with High Jump Kick, but gets deflected by Gyro Ball. Hawlucha tries to use Flying Press, but gets distracted by hail; Avalugg attacks and defeats Hawlucha with Gyro Ball. Serena is worried about the hail, but believes that Ash and Wulfric are evenly matched now.
Looking at Sawyer, Ash sends Talonflame, who launches Flame Charge on Avalugg, who recovers itself in hail. Avalugg uses Avalanche, dealing a lot of damage on Talonflame. Clemont warns Avalanche's power is doubled when the Pokémon using the move gets attacked. Talonflame manages to fly up and avoid Stone Edge attack. Talonflame hits Avalugg with Flame Charge, but Avalugg uses Avalanche, defeating Talonflame. Ash is frustrated and calls Talonflame back, then sends Greninja. Clemont and Sawyer think the tension in the air around Ash should allow Greninja to transform itself. Greninja charges on and evades Avalugg's Stone Edge and hits it with Cut. Greninja uses Aerial Ace, which gets deflected by Avalugg's Gyro Ball. Greninja fires Water Shuriken, though Wulfric claims it is no use, since Avalugg is spinning. However, Avalugg stops, since its legs got frozen. This allows Greninja to push away Avalugg using Cut. Clemont explains Water Shuriken froze when it hit Avalugg, freezing the legs. Wulfric admits that was a surprise tactic.
Ash urges Greninja to grow stronger, and Greninja syncs its mind with Ash, transforming itself. Bonnie is glad to see Ash-Greninja, but Sawyer notes he saw this form before, being enveloped in water. Ash-Greninja uses Aerial Ace, badly damaging Avalugg. Avalugg retaliates with Avalanche, hitting Ash-Greninja, a pain Ash senses as well. Sawyer is surprised, while Clemont explains Ash and Greninja are one and both will take damage. Ash's deep desire is to win this match, while Ash-Greninja looks at its Trainer. Ash-Greninja uses Cut and slices through Avalugg's Stone Edge, then damages Avalugg. Avalugg repeats its attack, which wounds Ash-Greninja, a pain Ash feels as well. Ash-Greninja uses Aerial Ace, attacking Avalugg and pushing it away. Wulfric comments how Greninja has this power, but has Avalugg use Avalanche, pushing Ash-Greninja away. Ash continues feeling the pain and has Ash-Greninja use Cut. Avalugg uses Ice Fang, freezing Ash-Greninja and slamming it away with Gyro Ball. With Ash-Greninja defeated, Ash faints, causing Wulfric to win the battle.
Ash wakes up, seeing he lost the battle. Wulfric points out water can adapt to its environment without changing its essence, something Wulfric can't exactly do. Wulfric points out a Trainer can only go so far unless they have deep trust in their Pokémon. Wulfric tells Ash that this is something he and Greninja failed to do, and until he learns how, he can't let him have the gym badge. Later on, in the Pokémon Center, Nurse Joy checks up on Greninja and reports Greninja took a lot of physical and mental damage, but will heal it back to normal. During the night, Sawyer decides to go and train for the Kalos League. Sawyer bids farewell to the heroes and promises to battle Ash at the League. While walking, Sawyer believes in Ash's victory, whom he admires, and promises to wait for his arrival. Ash visits Greninja and apologizes, thinking if he were calmer during the battle, he'd manage to draw out Greninja's power. Ash puts on his jacket and tells his friends he wishes to be alone for a minute, even if it is during the night. The next day, Bonnie visits Clemont and Serena, who have been expecting Ash, who has not returned yet. Serena worries, though Clemont thinks Ash will come back during lunchtime. Ash, however, is sitting in the forest, thinking about his recent defeat.