The real estate owner has responsibility to find the common guarantor.
For prevent in case the contractor doesn't pay the money or can't be contacted.
Guarantor conditions: "Japanese", "stable income"...
In case there is no Japanese guarantor, it is necessary to use the guarantee company. This guarantee company can be recommend by the real estate company.
(Even if the tenant is Japanese, if there is no Japanese guarantor, he must also use the services of the the guarantee company)