Salam o Alikum
Just resolved this issue in my own 2012 civic manual (140,000 km driven)
Buy Osaka green coolant (or any other brand of any colour but preferably green cplour as it's relatively easy to see)
Have ur car engine bay cleaned mota mota at service station so u can spot any leaks
Add coolant into radiator and drive around
Leak spots will show up as green colour
Must see following 2-4 places:
1. Radiator cap
2. Radiator top is made of plastic and can get cracked
Check following
3. Water body (check by hosting car after driving it and engine is still hot) it in near bottom right side and any leakage of water should be visible due green colour of coolant
4. Water reserve bottle might have some leak
5. Last but not least any of the 2 rubber pipes and connecting places of these to engine / radiator
Hope this helps...