The episode begins with Ash and his friends, Serena, Clemont, and Bonnie, arriving at a Pokémon Center in Lumiose City. They are excited to rest and prepare for the upcoming Kalos League. As they enter, they notice a commotion outside. Ash is eager to see what's happening and rushes out, followed by his friends. They find a large crowd gathered around a battle between two trainers, Alain and his Charizard, and a trainer named Mairin with her Chespin.

The battle is intense, showcasing Alain's skill as a trainer. Charizard uses powerful moves, overwhelming Chespin. Mairin, however, shows determination and tries to encourage her Chespin to keep fighting. Despite her efforts, Alain's Charizard ultimately defeats Chespin, leading to Mairin's disappointment. Ash watches the battle with admiration for Alain's strength but also feels a sense of empathy for Mairin.

After the battle, Ash approaches Mairin to comfort her. He encourages her to keep training and not to give up on her dreams. Mairin expresses her admiration for Ash and his friends, particularly noting how they support each other. Meanwhile, Alain and Ash exchange a few words, hinting at their rivalry and mutual respect. Alain mentions his goal of becoming stronger, which resonates with Ash.

The scene shifts to a training montage where Ash and his friends prepare for their own battles. Ash is particularly focused on improving his skills and strategies. He practices with Pikachu, while Serena works on her Pokémon performances, and Clemont tinkers with his inventions. Bonnie cheers them on, showcasing her unwavering support for her friends.

Later, the group decides to visit a nearby park to relax. While there, they encounter Mairin again, who is training with her Chespin. Inspired by Ash's earlier words, she is determined to improve. Ash offers to help her train, and they engage in a friendly battle. Mairin's Chespin shows growth, using new techniques learned from their practice. Ash praises her progress, boosting her confidence.

As the day progresses, Alain arrives at the park, and a competitive atmosphere builds between him and Ash. They decide to have a battle to test their skills against each other. The battle begins with Ash sending out Pikachu and Alain using his Charizard. The two Pokémon clash fiercely, with Pikachu using Thunderbolt and Charizard countering with Flamethrower. The battle is dynamic, showcasing both trainers' strategies and their Pokémon's abilities.

During the battle, Ash's determination shines through as he pushes Pikachu to its limits. Alain, too, is focused and strategic, using Charizard's speed and power effectively. The crowd gathers, captivated by the intensity of the match. Just as it seems Ash might gain the upper hand, Alain's Charizard executes a powerful move that catches Pikachu off guard, leading to a decisive victory for Alain.

After the battle, both trainers show respect for each other. Ash acknowledges Alain's strength and expresses his desire to become stronger himself. Mairin watches the exchange, feeling inspired by both trainers' dedication. The episode concludes with Ash and his friends reflecting on their experiences, motivated to continue their journey and improve as trainers, while Alain and Mairin share a moment of camaraderie, hinting at their own growth and aspirations.

In the ending of "Rivals: Today and Tomorrow!", Ash and his friends witness a fierce battle between Ash and his rival, Alain. The battle culminates in a dramatic showdown where Ash's Greninja faces Alain's Mega Charizard X. Despite Ash's determination and the bond he shares with Greninja, Alain ultimately emerges victorious. The episode concludes with Ash reflecting on his journey and the importance of rivalry, while Alain expresses his own motivations and goals. The episode ends on a note of camaraderie, with Ash and Alain acknowledging each other's strengths and promising to meet again in the future.

As the episode nears its conclusion, the scene shifts to the battlefield where Ash and Alain are locked in an intense battle. The atmosphere is charged with excitement as the two trainers face off, each determined to prove their strength. Ash, filled with confidence, calls upon his Greninja, who has transformed into its unique Ash-Greninja form, showcasing a powerful bond between trainer and Pokémon. The visual spectacle of the battle is heightened by the vibrant colors and dynamic movements of the Pokémon as they unleash their attacks.

Alain, equally resolute, commands his Mega Charizard X with precision. The fiery dragon Pokémon roars, its wings casting shadows over the battlefield, as it prepares to unleash a devastating Flamethrower. Ash counters with a Water Shuriken, and the two attacks collide in a brilliant explosion of light and energy. The audience watches in awe, captivated by the display of skill and strategy.

As the battle progresses, both trainers push their Pokémon to the limit. Ash's determination is palpable; he recalls moments from his journey, the friendships he has forged, and the lessons he has learned. He believes in the strength of his bond with Greninja, and this belief fuels his resolve. However, Alain's experience and tactical prowess begin to turn the tide in his favor. The tension builds as both trainers exchange powerful moves, each refusing to back down.

In a climactic moment, Greninja launches a final Water Shuriken, but Alain counters with a powerful Dragon Claw from Mega Charizard X. The impact sends shockwaves through the arena, and as the dust settles, it becomes clear that Alain's Charizard has emerged victorious. Ash watches, a mix of pride and disappointment washing over him. He acknowledges Greninja's efforts, understanding that they fought valiantly together.

After the battle, the atmosphere shifts from competition to camaraderie. Ash approaches Alain, extending his hand in a gesture of respect. Alain, recognizing Ash's strength and determination, accepts the handshake. They share a moment of mutual admiration, both aware that their rivalry has pushed them to grow as trainers. Ash reflects on the importance of their encounters, realizing that each battle has taught him something valuable.

As the episode draws to a close, Ash and his friends, including Serena, Clemont, and Bonnie, gather together. They discuss the battle and the lessons learned, emphasizing the bonds of friendship and rivalry that have shaped their journey. Ash expresses his desire to continue growing and improving, vowing to meet Alain again in the future. The episode ends with a sense of hope and anticipation, as both trainers look forward to their next encounter, ready to face new challenges and adventures ahead.

In the episode "Rivals: Today and Tomorrow!" from Pokémon season 18, there is indeed a post-credit scene. After the main events of the episode conclude, the scene shifts to a serene setting where Ash and his friends are enjoying a moment of relaxation. The atmosphere is light and cheerful, reflecting the camaraderie they share.

In this brief scene, Ash is seen playfully challenging his friends to a Pokémon battle, showcasing his competitive spirit and enthusiasm for training. Serena, with a smile, expresses her excitement to join in, while Clemont and Bonnie cheer them on, adding to the lively ambiance. The scene captures the essence of their friendship and the ongoing journey they share in the Kalos region.

This light-hearted moment serves as a reminder of the bonds they have formed and the adventures that lie ahead, leaving viewers with a sense of anticipation for what is to come in their journey. The post-credit scene encapsulates the themes of rivalry, friendship, and the joy of Pokémon battles that are central to the series.

Team Rocket appears in this episode with their usual antics, attempting to steal Ash's Pokémon during the battle. Their presence adds a comedic element to the intense rivalry between Ash and Alain, while also serving as a reminder of the ongoing challenges Ash faces beyond just battling rivals. Their failure to capture Pikachu also reinforces the bond between Ash and his Pokémon.

Serena's performance in the Pokémon Showcase is a pivotal moment for her character. It reflects her growth as a Pokémon Performer and her confidence in her abilities. The pressure of competing against her rivals, particularly against her friend and rival, Shauna, forces Serena to confront her insecurities and ultimately embrace her passion for Pokémon Showcases.

In this episode, Ash faces Alain in a highly anticipated battle that showcases their growth as trainers. The battle is significant as it highlights Ash's determination to improve and his desire to prove himself against a strong rival. Alain, with his powerful Mega Charizard X, represents a formidable challenge for Ash, pushing him to strategize and adapt his battle style.

Ash's relationship with his Pokémon is central to the battle against Alain. His deep bond with Pikachu and the trust he has built with his other Pokémon allow him to execute complex strategies during the fight. This emotional connection motivates Ash to push his limits and inspires his Pokémon to perform at their best, ultimately affecting the battle's dynamics.

During the battle, Ash employs a mix of offensive and defensive strategies, utilizing Pikachu's speed and agility to outmaneuver Alain's Mega Charizard X. Alain, on the other hand, relies on the raw power and versatility of his Mega Evolution, showcasing his experience as a trainer. The clash of their strategies highlights their contrasting styles, with Ash focusing on teamwork and adaptability, while Alain emphasizes strength and precision.

The episode "Rivals: Today and Tomorrow!" from Pokémon, season 18, is generally considered family-friendly, as is typical for the series. However, there are a few elements that might be considered potentially objectionable or upsetting for some children or sensitive viewers:

1. Rivalry and Competition: The episode features intense rivalry between characters, which may lead to feelings of frustration or disappointment, especially for younger viewers who may be sensitive to conflict.

2. Emotional Moments: There are scenes that depict characters feeling pressure and anxiety about their performance in battles, which could resonate with children who experience similar feelings in competitive situations.

3. Loss in Battles: Characters face defeats in Pokémon battles, which can evoke feelings of sadness or disappointment. The emotional weight of losing can be impactful for viewers who empathize with the characters.

4. Character Tension: There are moments of tension and conflict between characters that may be unsettling for some viewers, particularly those who are sensitive to interpersonal disputes.

Overall, while the episode contains themes of rivalry and competition, it is presented in a way that aligns with the show's overall positive and adventurous tone.