If I die before my wife can she collect my social security benefits, once she turns 62,
Even if she is:
Not a us citizen
Decides to move back to Japan
and surrenders her green card.
Actually, your wife could potentially qualify for widow's benefits as early as age 60 in the event of your death. And, since the U.S. has a Social Security totalization agreement with Japan, moving to Japan would not cause your wife to lose her widow's benefits assuming that she's a Japanese citizen.