let me just add a bit about renting an apartment in Tokyo.
If you come to Japan with a working holiday and is still not sure if you land on a long-term job maybe you can consider sharehouses first.
If you rent your own place without a company backing you up, it will be a bit costly.
Let say , Leopalace 1K in Central Tokyo ( it is possible that it is much more )
I will post this in yen:
Rent ( average )/month - 50,000- 60,000yen
Deposit ( minimum a month ) - 1 month rent --> refundable
Reikin/Thank you fee - minimum of 1 month rent -> none refundable
agent fee - minimum of 1/2 month of the rent
so for moving in you need to pay at least 4 months of the rent.
another option is to check into sharehouse. lately sharehouse have been popping up in Tokyo . Both foreigners and Japanese are opting for it rather than pay the insanely expensive real-estate fees.
you might want to check into Sakura houses, Villa Saranda and others.