thats a bit low. it should give you around 14-15+ .
There can be many many reasons for low fuel avg. Here are some tips.
Drive with light foot, don't accelerate hard from stops.
Have you checked and changed its engine oil ? for JDMs you need the highest quality fully synthetic engine oil and equally good quality filter. if odo is less than 40-50k . then get Zic A+ 5w30 . if above, then 10w40
the air pressure in your tyres should be around 34psi (not the old pakistani one-for-alll solution of 30psi )
change/clean air filter and also get you transmission oil checked.
Checkk your plugs and also throttle body service.
If you are in lahore, then for all above oil/filter/air filter/throttle body etc. I go to "Filter House" shop. They are experts in JDMs and advise best depending on how much you ready to spend. I would advise dont compromise on engine oil and its filter.
They have multiple shops, 1 on ferozpur road, 1 in model town and 1 on montgomery. I go to ferozpur road one. They will check and advise.
Hope this helps.