Disclaimer : I dont own Pokemon or it's characters and I never will :Credit for the cover goes to said person who made the fanart
A team battle takes place with Ash and Serena against Clemont and Korrina

We join our heroes as they do something fun on the 2nd last day of their journey together,Ash and Serena battle Clemont and Korrina and the battle is nearing it's end as each trainer only has one Pokémon left:Ash has Greninja left,Serena has her recently evolved Delphox left,Clemont is left with Luxray and Korrina is left with Mega Lucario.

Ash : Greninja,Battle Bond now! (Greninja gets enveloped by a torrent of water revealing Ash-Greninja.)

Serena: Delphox,follow by copying Greninja's stat changes with Psych Up(Delphox suddenly blazes brightly.)

Clemont : Luxray I know this is risky but combine Wild Charge with Volt Tackle against Greninja!

Korrina : Lucario use Bonerush on Delphox!

Ash : Greninja, use Double Team and intercept Lucario's attack,you know your ultimate move,hit Lucario with it!

(Greninja makes doubles of himself leaving Lucario confused and then grabs the giant water Shuriken on it's back,then hurls it at the confused Lucario and landing a hit,then dust envelopes Lucario as it gets hit.)

Serena :Delphox now intercept Luxray by combining Overheat and Fire Blast!

(Delphox fires an Overheat powered Fire Blast at Luxray who stops in his tracks as an illusionary Greninja appears in front of him and he gets hit with Delphox's Combination attack leaving him in a cloud of dust next to Lucario)

The dust settles and both Luxray and Lucario have swirls for eyes with Lucario having reverted to Regular Lucario.

Clembot : The win goes to Ash and Serena!

Greninja reverts back to regular Greninja with Delphox standing next to him.

Ash suddenly gets enveloped by Serena in a huge hug.)

Serena : Ash we did it,we beat them in a team battle!

(She was so happy that she pulled Ash Closer by his collar and planted a hard kiss on Ash's lips.)

Ash blushes red like a tomato and his eyes grow to the size of saucers,but he quickly closes his eyes in total pleasure and finally kisses back.

Serena pulls back after a minute long kiss and smiles brightly at Ash who in return smiles back.

Ash: Serena,will you be my girlfriend?

Serena: Yes Ash I'll be your girlfriend! I've waited so long for you to ask that question.

Ash : You just made me the happiest boy alive! (They kiss again and 5 years later they get married and both achieve their goals together and have a happy life further) \The End/