I've got a job in Japan. My working location willl be Shinondai or Yokohama. My salary is JPY200000(after tax)

is the salary enough for me. I'm a bachelor and going to stay with my batchmates only (on sharing basis)

Yeah. You'll be fine. You can't party every night, but you will have enough to live on. If you try hard, you can even save some.

Gee... Adam... Report It

If you are going to live in Yokohama, might be a bit tough.
It depends on how much the rent is gonna be...

*Rent -- 50,000yen if you share
*Gas, water, electricity -- 12,000yen if you share
*Food -- 20,000yen if you cook. If you eat outside often, then probably 50,000yen or more...
*Internet -- 2,000yen

If you buy new electric appliances and furniture when you move in, it's going to cost a lot...
Also if you are a party person on weekend, you need to pay extra...
As long as you don't live in the lap of luxury, 200,000yen is enough though.

A few things to keep in mind:
Train and bus costs, most companies comver the cost of trains and bus but it depends on the actual specifics of your contract.

National and local taxes: There are yearly national and local taxes. In my experience, I always had to pay more on top of what was already taken from my paycheck. This also is dependant on your terms of emplyment, meaning is your contract on a year to year basis or on a medium 1.5 years or more basis. More details to inquire about with your new employer.
The amount of taxes I had to pay really surprised me.
In general, you seem to have enough to live one, and as mentioned you can also save some money.

If you are getting accomodation subsidised by the company or the share you mentioned is not too onorous (say, under 50,000 yen per month) and the company pays your commuting costs, then it's not too bad if you are in an entry-level position.

One major factor that will make or break your financial situation is bonuses. With a typical 2-month bonus every 6 months, you will definitely be comfortable assuming you're not a party animal, but without the bonus you will need to economise a bit.