I got a lot of messages from people that say they are confused about Serena being Latias so I wrote a separate backstory for her! However, in order for most people to be on the same page I conveniently introduce this prologue to you readers as a third chapter! Perhaps some of you have already read this backstory but a good scenario never gets old!
A boy and his two loyal friends were finally leaving Alto Mare City - the boy was following his dream to become a Pokemon Master.
Before he boarded the boat, a girl ran up to him. He thought he knew who she was - until she kissed him on the cheek - then he began doubting. But a true Pokemon Master doesn't have a place for love in his heart for he is devoted to his only dream, and the dream will lead him farther than any love ever will. After all, even the most strong relationships come to an end, and his friendship with Brock didn't become an exception. Eventually, each person has to choose his own path, so the Chosen One continued his journey in solitude , even though he befriended a lot of various companions later down the road.
Is he a foolish dense character as many of his numerous haters like to portray him in their spiteful speeches ?
Or is he a mysterious living model of reverence and altruism as his even more numerous friends claim?
If we were to ask the Chosen One himself, he would probably just smile without giving a direct answer...
But if we were to demand an answer from his mother she would probably tell us the most truthful answer.
The Chosen One is neither a dumb simpleton who cannot grasp the concept of romance nor is he a heartless melancholic who denies the vital importance of affairs de coeur.
He is the Don Quixote of our days, a youthful man who worships his Dream regardless of how achievable it is in reality.
He is the One who Aims To Be A Pokemon Master.
And that is all there is to it.
Latias cried day after day when Ash left. With her brother dead, there was no purpose anymore in her life. She didn't care about the Alto Mare city anymore - she just wanted to reunite with Ash. Bianca and Lorenzo saw how depressed she was - and they made a decision. Latias's destiny was to pursue her dream - the Chosen One. After all, Lorenzo and Bianca were capable of defending the Soul Dew of the Secret Garden themselves. Bianca promised that she would become a Pokemon trainer of immense power so nothing would threaten Alto Mare again...Still, the death of Latios was something that no words could compensate.
Since Latias could transform into a human form, it was decided that she must learn human speech to blend into a crowd, because there would have been a lot of people who would want to capture Latias as a Pokemon and force her to battle against her brethren for the sake of a questionable amusement. But since Ash believed this was good, Latias didn't condemn Pokemon battling even though deep in her heart she always thought it was a cruel way of humans to entertain themselves showing off their superiority as "Masters of Pokemon". What a lie! Arceus is the only Master! But people had failed to realize that for many millienia. And Latias just had to accept it for granted.
After months of training and mentorship with Bianca and Lorenzo and interacting with the city dwellers in the streets and the local art school, Latias (disguised as Bianca's "cousin") finally learned how to act like a human, how to talk like a human, how to think like a human. Since Ash's departure, she had never once transformed into her Pokemon form, fearing that her "humanity" would fade away, growing to despise and hate her pokemon essence - she just wanted to be a human, like the Chosen One. Every night she had dreams of the Chosen One choosing her as his true love. She also knew that the humans would never accept a pokemon as their equal despite what all of the Trainers loved to boast about - If Pokemon were truly equals to humans, why couldn't Pokemon be Human Trainers ? Or Human Masters? Why couldn't a Pokemon become a Regional Champion?
Latias could not answer these questions. So her only remaining option was to embrace her humanity as a salvation and to even forget how her Pokemon origin. At first she was conflicted, but soon, in a year or so, she too, acquired that arrogance stemming from superiority towards ordinary Pokemon - she of course, "accepted them as equal friends" but of course she never hesitated to use them as convenient tools, convincing them to "be sheltered in the pokeballs" - the true Pokemon prison. Arceus must be weeping when he looks at how enthusiastically the Pokemon were accepting their chains! But Latias laughed, considering herself a pokemon no more but a human girl. Soon she began feeling tired of wearing Bianca's face, she wanted to be special, she wanted her own identity.
In a sudden mood of kinship guilt she released all of her Pokemon...And left Alto Mare without a trace, deciding to travel anonymously because she didn't want to wear the weight of another person's identity, also leaving forever the place that made her so happy, and in the end left her so sad.
One sunny day, in Pallet town, a girl in a brown cape with a hood covering most of her face knocked on the Ketchum family house.
"Hello! Come in" A young woman invited the girl inside. The girl didn't reveal her face but entered.
"Hello. I would prefer to stay anonymous. But I would would like to know where Ash is. This is Ash's house, isn't it? It took me a very, very long time to find this place."
"Well, Ash has just left today to explore the Kalos region to Lumiose city, you know, typical League stuff. I assume you're a friend of his? I'm his mother, you can call me just Delia." Delia stretched out her hand.
"Uh...Yes? Kalos, you say...I see..." The girl accepted the handshake.
"Sorry for being so straightforward, but could you tell me, is there a girl that Ash loves?"
"A girl that Ash loves? Hmm, can't remember anything like that...Although, when Ash was a little kid, there was a girl he was really good friends with..And she was also from Kalos. Oh, by the way, here's a photo of them two together.."
Delia showed the girl a photo of Ash and a blonde girl in a strawhat, both preschool aged.
"What's her name?"
"It was Serena...Ash doesn't know about this - and he shouldn't know - but she died a few years ago from a disease...She sent this to us right before her death..You're looking for Ash, right? If you meet him, please give this to him - it's a handkerchief that Ash used to tie up Serena's wounds with."
It was a blue handkerchief with barely noticeable words "from Serena" sewn in pink silk in one of the corners.
"I'll gladly do that..." The girl accepted the handkerchief. "Goodbye, Delia."
"Hmm, wha-
Where did that girl disappear to?"
The girl was nowhere to be seen, as if she had teleported.
Even though Latias hated doing this, there was no other way. She had no second to waste...She could only teleport on ~30meter distances, so she had to transform to fly to Kalos. She was flying on the wings of her dream. She crossed continents and oceans but she didn't even notice. She landed in the outskirts of Lumiose city.
At first, she adjusted herself to look like an older version of the deceased Serena image from the old photo. Next, she went to the local professor to get a pokemon. She decided to disguise as a rookie trainer.
She activated her telepathy mode that Latios had taught her a long time ago - it seemed like that had happened centuries ago. How old was she actually? She forgot and she didn't want to remember. She searched for Ash, scanning the city for his Psychic-Aura waves, and then she tracked him down. She ran to that direction.
Her heart was about to explode. She could see Ash from afar, and she quickly thought through her impersonation plan as she approached her Dream...
They had travelled together through the whole Kalos region, but Serena never made any real progress in a romantic relationship with Ash. But she was not sad, oh no. Just being in Ash's presence made her eternally happy. When time came to part their ways, she gave him a kiss of her sincere love, she promised him that she would become a more attractive woman. For Ash she was ready to become anything. Latias knew that they were destined to meet again - as long as they both believed in their Dream. Even so, Latias felt herself so distant from Ash, despite being able to get so close...
Delia never really understood what happened, she just thought that Serena was just a girl with the same name as Ash's childhood friend who looked similar.
Latias had created a new identity for herself, just like she wanted to. She completely rejected her Pokemon essence.
Consider this as a sort of Serena's/Latias's flashback! Like a filler episode in the middle of a plot arc!