The festival name in Japanese is "Kumihama Kaki-sakana matsuri(久美浜 カキ・魚まつり)". If you would like to try winter season's seafood, this is a good oppotunity! They serve grilled oyster which catched in Kumihama bay and soup with crab, those are for free of charge! *Although it doesn't mean you can eat as much as you want.*
Date: first Sunday in December
Time: 9:00-14:00
Access:
From Kumihama station(久美浜駅) or Shotenkyo station(小天橋駅), take a city bus line called "Minatosen(湊線)" and get off at "Minatokobashi(湊小橋)" and walk 10mins.
Bus fare:200yen/single.
Location: Marine Plaza, 1664 Minatomiya Kumihama, Kyotango, Kyoto(京都府京丹後市久美浜町湊宮１６６４ マリンプラザ)