>>19221377I suggest these:
The Road to be a Pokemon Master: Kanto Arc
https://www.fanfiction.net/s/10065575/1/The-Road-to-be-a-Pokemon-Master-Kanto-ArcBasically a "what if" scenario where Serena never leaves for Kalos and is a retelling of the Kanto arc with Serena as a companion.
Serene Phoenix: Reborn
https://www.fanfiction.net/s/10304921/1/Serene-Phoenix-RebornA different take on the XY series, where Brock and Shauna are traveling companions, Charizard comes along to Kalos, N gives As a mysterious egg to take care of, and Ash's rival is an OC named Axel (if you're not into OCs, which I assume you aren't).
The following aren't very much about Ash and Serena as they are about the whole gang, but I think you'll enjoy them nonetheless.
Tradiion Together
https://www.fanfiction.net/s/9948599/1/Tradition-TogetherThe whole gang gets together to celebrate qt Christmas times in a Pokémon Center, being stuck there due to a snowstorm.
Dear Friend
https://www.fanfiction.net/s/9959646/1/Dear-FriendMy personal favorite. It's Holiday season in Kalos, but a few days before Christmas, Ash almost forgets to write Christmas letters to his previous companions and friends (including Paul, of all people). When he does remember to write...well, see for yourself.
I hope I helped.
