The development for the first-generation Boon was led by Toyota chief engineer Tetsuya Tada. For the Japanese domestic market, the Boon were available with 996 cc and 1.3 L engines. The major difference between the Japanese Boon and Sirion are automatic version where the gear-changing located beside the steering on the dashboard and the handbrake below the steering. Both the Japanese Boon and European Sirion were offered in both front-wheel drive and four-wheel drive versions. A 936 cc turbocharged version with four-wheel drive was also available, known as the Boon X4.