Now, in Japan,Currently smoking is prohibited in Japan for people whose age is belowunder 20.

The reason for this rule is mainly thatbecause smoking is bad for your health and it spoils the teenager's futurcan ruin the future of young people.

However, it's the same forBut in my opinion, it's also harmful to adults.

Smoking can causes lung cancer orand other respiratory diseases, andbut some people just can't ceasestop smoking because of their nicotine addiction.

ActuallyIn fact, my father is a smoker, and h. He often saidys "Don't smoke" because it has no merits, onlyis a waste of money and shortens your lifespan.

Therefore, I feel that restricting smoking will have a positive effect on people's health in Japan.

Smoking Shouldhould Smoking be Made Illegal in Japan?

You are asking a question here, therefore these words should be switched.

Now, in Japan, sSmoking is prohibited for people whose age is below 20 in Japan.

You can still add the "now" here, I just don't think that it is necessary because you're writing in the present tense

The reason for this rule is mainly that smoking is bad for your health and that it spoils the teenager's future.

You need some form of article or pronoun before "health" here

However, it's the same for adults.

This is correct! "It's the same for adults, however." Is an alternative

Smoking causes lung cancer orand other respiratory diseases, and some people can't cease smoking because of nicotine addiction.

Or is incorrect here because using "or" means that it is either of the two, and not both.

Actually, my father is a smoker, and he often said "Don't smoke" because it has no merit, only a waste of money and lifespan.

Therefore, I think restricting smoking will have a positive effect on people in Japan.

You're expressing an opinion here, therefore say that you think something is the case