BRO WHAT R U TALKING ABT BRO?! PLS GOD NO, SOMEBODY GIVE ME SPOILERS
ryuka feiya (jellyfish) is called the ruler of the fog sea and her powers are related to memories so she enclosed the whole place in her fog and the people inside it lost most memories (yoohyun lost the past year or maybe a bit more i think)
BRO WHAT R U TALKING ABT BRO?! PLS GOD NO, SOMEBODY GIVE ME SPOILERS