This Raichu is an -type Pokémon owned by Amber Ryan. He's the third Pokémon she caught in Kanto.
As wild Pokémon
Amber stooped in Viridian Forest to have a little picnic, when somebody has stolen her apple. She later found out that it was a wild Pikachu, and wanted to punish him. She sent Pidgey for a battle, however he was quickly defeated by Pikachu, who ran away with Amber's apple, full of joy. She was angry, but forgot about this accident and walked forward. Pikachu was dazzled by her battle style and became curious about Amber, and followed her through the forest, but fell off a tree and was spotted. Amber recognized him, though she didn't start a battle again, but only stared at a Pokémon. Pikachu ran a few circles around her, and pointed on a Poké Ball on Amber's belt. She was surprised that he wanted her to catch him. She threw a Poke Ball in him, and Pikachu was succesfully captured, much to Amber's astonishment.
As a Pikachu, he was really energetic, curious about almost everything and self-determined at one time, but also loyal to Amber, helping her to win some difficult battles. When she asked Pikachu to evolve into Raichu after being beaten by Lt. Surge, he showed his determination to win and evolved. After evolution, Raichu became more serious and calmed down a little, although his optimistic attitude and loyalty to Amber still remains with him.