Japanese passport holders can request a visa on arrival if they have not had time to apply for the eVisa before departing. However, they should note that this option entails waiting for a long time at passport control once they enter Tanzania.
They have to carry the amount of money needed to pay the processing fee in cash and have all of their original documentation to clear immigration control.
If the application is not approved on arrival due to missing documents or any other problem, the Japanese traveler will be denied entry and will have to return home.
With the eVisa, the process is much more convenient, has fewer risks and drawbacks, and is a preferred option for Japanese citizens.