When exactly are people considered an adult in Japan?

Question:

It seems people can buy, you know, like porn when they are 18 or over in japan. Then, does it mean they officially become an adult at the point they turn 18?
Well, how about tobacco, alcohol and voting right?

Thank you.

Answer:

The age of majority in Japan is 20. Age 20 is when one can legally purchase alcohol, tobacco products, vote. Age 20 is adulthood in Japan.

There are exceptions, for example,
By prefectural laws, the age of consent in Japan is 17-18.
At 18 age, things like purchasing "adult" material is legal.