During your time in JutsuOnline you will sustain injuries in combat, losing health points (HP). In order to regenerate your health, you will have to visit your respective village's hospital and talk to a Medical Nin at the cost of Ryo. You can also regenerate your health if you are a medic yourself or receive medical treatments from other players who have access to the medical talent path.
If your health is reduced to zero and your life is not spared within time, you will respawn in your village's hospital.
Each technique you perform will be at the cost of chakra. It is important that you conserve your chakra as it can take up to five minutes (the amount of time is reduced depending on your seal speed status) to regenerate. In order to regenerate your chakra, you will have to use the 'Rest' action which can be found in your Jutsu Book (P).