ProudFrenchJap!
Registered Users (C)
You certainly can leave, but you have to LIVE in the US and not elsewhere. The determination is made based on number of days you stay outside the US by CBP each time you cross the border.
My uncle is a Japanese Citizen and green card holder, he lives and travels constantly between the two countries. More like staying in Japan 1/3 of the year and the rest in the United States.