Toyota yesterday opened the order books for its smallest hybrid to thousands of space-conscious, fuel-weary Japanese buyers. More then 60,000 buyers have signed up to purchase the 83-mpg Aqua subcompact hybrid, which is expected to retail for $22,000 in Japan. Known as the Prius c to the rest of the world, the 1.5-liter hatchback is the same length and width as the pint-sized Yaris, but a little bit shorter to increase aerodynamics.