The stool would be designed with clean, minimalist lines, and made of sturdy materials such as metal. The base of the stool would be designed to mimic the shape of a traditional Japanese torii gate, with two posts on either side of the seat.

The koi design would be incorporated into the seat of the stool, with koi swimming towards each other in a circular pattern. The koi would be depicted in shades of blue, gold, and white, representing their symbolic meanings of perseverance and determination.

The base of the stool would be painted in a deep red color, representing the courage and passion of the samurai warriors who followed bushido. The torii gate shape of the base would be enhanced with additional design elements such as cherry blossom motifs or kanji characters that represent the principles of bushido.

Overall, a stool inspired by bushido with koi that change into a dragon print would be a powerful and meaningful addition to any space. Its combination of traditional Japanese symbolism and modern design elements ensures that it is both unique and timeless.