requirement by the immigration office

Hi, Me and my five friend has planned to study at Kanrin Japanese school in Yokohama and is now in middle of filling in all documents. Now do we have a little problem. The japanese immigration office wants us to have 20k USD on a bank account. Its alot money and all of us can't meet up with the requirement.
We have asked around and nobody have any more information. I was wondering if anyone that have studying in Japan can maybe provide us with more information

Yes that is a standard requirement for a student visa application (or in the COE), the main reason is as a student you OR a family member will defray all your costs while in Japan. The price varies on how long you plan to stay, but Immigration wants to see at least 15-20K USD.

okay, I'm gonna stay half a year. Is that the lower or higher part of the intervall?

Don't take my word on it, because things seem to vary a lot from place to place, but roughly around 9-10K+ for 6 months and 20K+ for 12 months (1 year) (all USD) is usually a standard.