The device that connects electricity to the car is an EVSE. It seems that you are using a Wallbox branded unit. It has maximum amount of electricity it can provide based on its rating and the rating of the circuit it is on. Check both of those to learn if it is capable of charging at 6kW.
However, I am somewhat confused by your post. The following information may help clarify. Apologies if this is redundant.
In the USA:
Level 1 charging is at 120V.
Level 2 charging is between 208 to 240V. (Japan is likely at 200V.)
Both the above use the same J1772 plug.
The charger is in the car. Two versions were used by Nissan, rated at 3.3kW or at 6kW. The typical draw by the 3.3 is 16A, by the 6 is 27A. Nichicon is the only manufacturer of these that has been mentioned on this forum.
Edited to correct the units.