The Semi-Final Frontier! (Japanese: シンオウリーグ準決勝！ダークライ登場！！ Sinnoh League Semi-Finals! Darkrai Appears!!) is the 32nd episode of Pokémon: DP Sinnoh League Victors.
Ash is at the field, facing Tobias at Semi-Finals. Tobias sends his ace, Darkrai, making James and Meowth very interested, but Jessie orders them to get back to work. Ash sends Heracross, who starts with Hyper Beam, but collides with Ice Beam. Heracross uses Horn Attack, but using Dark Void, Darkrai puts Heracross to sleep. However, Heracross' Sleep Talk causes it to use Horn Attack while asleep, making an impact on Darkrai. Unsuspected, Darkrai uses Dream Eater to defeat Heracross in sleep. James and Meowth are surprised, while Jessie orders them to sell stuff, but they get interest from other people about Darkrai goods.
Ash calls Heracross back and sends Torkoal. Torkoal uses Flamethrower, but Darkrai uses Dark Pulse and cancels the move, causing Torkoal to be defeated immediately. Ash calls it back and sends Gible. Darkrai comes close, though Gible's Rock Smash pushes it away. Darkrai retaliates with Ice Beam, but Gible dodges. Gible uses Draco Meteor, but Darkrai evades the attack and uses Dark Pulse to defeat it. Meowth hopes the twerp changes his tactic. Jessie demands to know when is he on the twerp's side, so Meowth explains that if the twerp beat them and now this Tobias beats the twerp, it proves they might as well side with the twerp. Ash calls Gible back. Tobias admits that any Pokémon attacked by Draco Meteor would be defeated, except his Darkrai. Ash sends Sceptile to battle.
Darkrai uses Ice Beam, but Sceptile uses Quick Attack and moves away. Darkrai dodged and attacks with Ice Beam. Darkrai uses Dark Void, putting Sceptile to sleep. Darkrai uses Dream Eater and affects Sceptile, but hearing Ash to wake up, Sceptile is awake. Using Leaf Blade, Sceptile immediately defeats Darkrai. Tobias calls Darkrai back and admits Ash has proven himself in the spot of the Semi-Final. Tobias is somewhat surprised, but sends his Latios, who swoops down. Sceptile uses Leaf Blade, but gets defeated by Giga Impact. Ash calls Scpetile back and sends Swellow. Swellow starts with Quick Attack, but Latios dodges. Swellow dives down and uses Aerial Ace, but gets defeated by Luster Purge. Ash calls it back and sends his Pikachu, knowing in mind they will not give up.
Tobias tells Ash his fighting has earned respect, but also tells that this is the final battle. Pikachu starts with Quick Attack, but misses. Pikachu uses Volt Tackle, but gets countered by Giga Impact. Latios uses Giga Impact, negating Pikachu's Iron Tail. Latios goes to finish using Luster Purge. Latios misses and finds Pikachu at its back, then uses Thunderbolt to electrocute it. Latios attempts to get him off, but fails and gets hit by another Thunderbolt. Latios uses LightScreen, causing Pikachu's Thunderbolt to do less damage. Pikachu uses Thunderbolt even more, so Latios goes up and gets Pikachu in air. Latios uses Luster Purge, so Pikachu uses Volt Tackle. Though he sustains damage, Pikachu uses Iron Tail as well and makes a collision.
After the smoke clears, Pikachu and Latios are defeated. Since all of Ash's Pokémon are defeated, Tobias wins the Semi-Finals. Ash gets Pikachu and says that Pikachu fought well. Tobias thanks Ash for such a good battle. Dawn and Barry are sad, but Brock sees that Ash made to Top Four. Team Rocket also feel a bit sad, but turn back to selling goods. Later, Tobias used only his Darkrai to defeat his opponent and wins the League. At the evening, Tobias gets his trophy and everyone watches as the flame on the top of the arena is extinguished. Next day, Brock tells to Ash and Dawn the journey is not over, as Ash still wants to be the Pokémon Master and Dawn the Top-Coordinator. Brock is happy to see them with dreams, but wonders about his own. Barry also appears and admits Ash is a bit stronger than him, but needs to be much stronger, else Barry will defeat him in next battle, then leaves. Ash promises to be stronger, as he has to pursue his dream.
- During the opening when the name is revealed, the background music is changed.
- There is no Professor Oak's lecture at the end of this episode. Instead, a minute-long preview for the Best Wishes series is shown.
- Another episode has a similar English title as this episode.
- This episode marks the only time Ash has flipped his hat in the Diamond & Pearl series during battle.
- This episode's English title is a reference to the phrase the final frontier.
- This is the only episode of Pokémon Diamond & Pearl: Sinnoh League Victors that kept the entire Japanese music unaltered, including the title card music.
- This currently is the farthest that Ash has ever gotten in a Pokémon League, reaching the Top 4.
- After Tobias defeated Ash, in the scoreboard a Mismagius silhouette appears in place of Swellow's one. Also, the Torkoal and Darkrai silhouettes are slightly different from before.
- After Ash told Pikachu to use Quick Attack the first time, he said for Pikachu to use Volt Tackle. When it hit Latios' Giga Impact, it was Quick Attack.