How lightweight are japanese people? I don't drink alcohol, so i don't know how long i could last, but based on stereotypes, i remember that the japanese are considered to have very little tolerance.
As a general rule, the higher your body weight the higher your alcohol tolerance. Alcohol gets distributed throughout your whole bloodstream after all. However there's also an element of how used to it you are and there are some pretty hardcore drinkers in Japan.
In manga there always seems to be somebody who immediately gets drunk because it's manga...