"The reason we participate in this memorial ceremony is to let people know why the Sewol ferry disaster happened and why the children were not rescued," said Kim Soon-gil, who lost her child in the disaster.

On the morning of April 16, 2014, the Sewol sank with 476 passengers and crew on board. Of the 304 people killed, 250 were students from the Danwon High School in Ansan.

The scenes of the 6,800-ton vessel sinking on live TV stunned the country. Disbelief turned to outrage as it emerged the captain and crew had abandoned the ship, and that the children were told to stay in the cabin and wait for rescue.