The 26 km/l figure is from Japan's 10-15 test; that test does not reflect normal driving habits and realistic conditions (for example completely flat road). For comparison, a lean burn 6th gen Civic can achieve 30 km/l on that cycle; achievable for a hardcore hypermiler, but impossible for a routine driver.
That said, you can gain something like 20+ in local driving by hypermiling; it will be almost easy without A/C use. The greatest enemy of fuel economy in city driving is brake usage; try to minimize braking and conserve momentum. I will give you a few pointers. For more details, check the link in my signature.
__You will need to time your trips; start your commute early in the morning, and delay your return home a little bit to avoid the worst of the rush hour traffic.
__Anticipate traffic and road obstacles, so that you can minimize brake use. If you know that there is a u-turn or similar ahead in your lane, find the earliest opportunity to change your lane. If you see an intersection/roundabout/red light ahead, use engine braking instead of your brakes (more on this later).
__If you have to stop for more than ~10 seconds, shut the engine off.
__If you have to use A/C, use it when the car is in a steady cruise/engine braking state. Turn it off during acceleration. I usually don't turn the A/C on in my Civic below 32 km/h (minimum speed for 3rd gear).
__Use a slow acceleration rate, just barely keeping up with traffic in the slow or middle lane. After you have some practice, there are some advanced acceleration techniques used by hypermilers that you can use.
__When you get the opportunity to coast, such as a gentle down slope, put your car in neutral, and let it coast as far as road and traffic conditions allow. This will give you a significant boost on fuel economy.
__During engine braking, the engine is in fuel cut mode under some parameters. The car should be above a certain speed and RPM. I will give you an example; my Civic needs to be above ~1200 RPM and ~35 km/h to be in fuel cut, IIRC. During an engine braking maneuver, I downshift to D3 at ~50 km/h, and to 2 at 40 km/h. I usually just shift to neutral and shut the engine instead of shifting to 2, but that is another story. Don't shut it off in your Vitz, because it can cause serious transmission damage.
Start of with these tips, and see what you get.