The biggest Spanish festival in Japan is held annual at the end of November and attracts over 100,000 people over the course of the weekend. Over 30 vendors sell Spanish food and drink, and on the stage you can watch flamenco dances and other traditional performances. Detailed listing of the vendors can be seen on the website (Japanese only)
Event details are taken from official sources whenever possible. It is always prudent to check the official event website before attending to make sure that there have not been any changes. If you know of an error in the calendar, then please let me know through the contact form.