Deep in the forest, hidden from any Trainer, is a village filled of the electric mice line of Pikachu. Here, they have made their own, living peacefully in the wild. Though, predators attacking, and rival groups starting wars weren't unheard of. Such is the way of survival.
Within this humble home is a Pikachu named Thunder. A hero to many, and a rival and enemy to others. Here, the young mouse strides to be the best, and protect the village from threats within and outside.
A Raichu seeks to also be the best, through power, control, and a ruthless brute. The two have butted heads ever since the day they were born. Lifelong rivals and enemies.
Every thousand years, the Legendary God of Thunder, comes to the village, seeking the lucky one to take with him, to train in the ways of being a warrior; to become the next Thunder Warrior.
It has been just a thousand years already, and the Pikachu and Raichu in the village train hard, wishing that they would be picked for greatness.
This is Thunder's story.