Koji Takahashi is a graphic designer who works in Nintendo EAD division. He is well known for working in the Animal Crossing and The Legend of Zelda franchises.
His first work is the game The Legend of Zelda : The Wind Waker where he was a character designer. After this, he started working at the Animal Crossing series was a character designer and worked the two Nintendo DS Zelda games. After Ryuji Kobayashi, the previous Art Director from the Animal Crossing series, went to work on The Legend of Zelda: Skyward Sword, he took his role starting with Animal Crossing: New Leaf.
Animal Crossing New Leaf Concept Art
Animal Crossing 3DS concept art