14 is the base age to be a travelling trainer who defeat gyms in my pokemon world. You live in unnamed island (Either I'll name Veta Island or Escelar region).
There are no gyms. Instead, the island annually holds a festival in which lugia (Togepi) / Ho-oh (Pichu) is respected. It is like; signed up trainers go defeat 4 four battle tents, enter the ultra tent for semifinals and then defeat the regions old protector, in front of the legendary.
You are an extremely energetic, 10 year old kid living in hometown, Prof. Blue Oak comes to the region to study some history during the festival and he stays in your hometown. You asked a pokemon to go on a journey, but he didn't give
because It would be dangerous (BLUE, RED & LEAF STARTED THEIR JOURNEY WHEN THEY WERE I4 IN MY UNIVERSE LOL), but seeing you help a wild togepi / pichu, he understood you and gave you that pokemon. He also signed you up for the competition. You go the journey, defeat tents, meet trainers from other regions ( tourists which include famous trainers ), defeat the local gang, find the summoning stone aqua / summoning stone flame and summon the legendary.
The stone gets stolen by the gang, you must also retrieve it.
+Lugia is now Water / Flying