If you are returning to your country during school vacations, or leaving Japan for travel, check "I am leaving Japan temporarily and will return" on your ED card, and present it at the airport（see here for a sample when filling out the ED card）.

If you fail to return to Japan within one year from departure, you will lose your status of residence. If your period of stay is to expire before one year from departure, be aware that you must return by that date of termination.

For details, check the Website of the Immigration Services Agency.