That doesn't work out in Germany.
Let's say you earn 2000€ (before taxes). After taxes you'll have around 1350€ (minus Lohsteuer, Kirchensteuer, Arbeitslosenversicherung, Rentenversicherung, Krankenversicherung, Pflegeversicherung).
If you're lucky you might find an apartment for 500€, so let's say we're lucky.
Then we still have 850€ per month. We probably have to pay a private pension as well (private Rentenvorsorge), let's say about 200€, so we still have 650€.

As I haven't lived in Germany for such a long time I have no idea how much I should calculate for food, phone, internet, car etc. .... Let's say another 400€.

So now we have 250€ left each month. (If I calculate with the 700€ that you suggested, I wouldn't have enough money to live! .....)
I'd have to save a whole year in order to be able to travel to Japan (or anywhere else).
And in reality you permanently have to buy other expensive things (new furniture, a new car and whatnot).

*sigh* .........................