A. You can obtain a trademark right by registering it with the Japan Patent Office.
In the U.S., unregistered trademarks, such as common law trademarks, may have trademark rights, whereas this is not the case in Japan.
Even if you use your own trademark first, a third party will, in principle, have trademark rights if they register the same mark first. Once a trademark right is granted to the third party, even if you are the prior user, you will no longer be able to use the trademark (*1). In order to have trademark rights in Japan, it is necessary to file an application for trademark registration with the JPO and have it registered before others do. The JPO's examination period is 5 to 10 months (as of April 2022, by the JPO).
(*1) If a trademark that has been used in Japan without registration becomes well-known, it is possible to refuse the trademark owner's appeal to stop using the trademark. However, the user bears the heavy burden of proving that the trademark is well-known. Even if the trademark proves to be well-known, it does not prevent others (e.g., counterfeiters) from using the trademark. This is why many companies proactively apply for trademark registration.