Yofune-Nushi was a Japanese sea serpent of huge size that preyed upon the islands of Japan making the life of fisherman dangerous. They kept checking by offering it a maiden every 13th of June. One very brace maiden called Tokoyo equipped herself with a sharp knife and while she was waiting to be seized by the serpent. When it got close enough she stabbed its eyes and it died.
John and Caitlin Matthews, The Element Encyclopaedia of Magical Creatures, 2013, Yofune-Nushi, p 524