Why do the Japanese believe that if 'Doomsday' fish comes to the surface, it means disaster will follow

Recent sightings of the rare oarfish, popularly called the "Doomsday Fish" has left everyone talking and their brains boggling in speculation. This deep-sea creature which has a long, ribbon-like body and shimmering silver scales, has been spotted near the shores of Baja California Sur, Mexico, causing a stir on social media.
The oarfish's rare appearances near the surface have long been associated with forthcoming natural disasters, particularly earthquakes and tsunamis. This belief is also deeply rooted in Japanese folklore and has led many to wonder if these recent appearances are a harbinger of doom.
The oarfish has the nickname of "Ryugu no tsukai," or "sea god's palace messenger," in Japanese folklore. This myth traces back to the 17th century and says that the surfacing of the oarfish is a harbinger of future natural disasters. The myth received strong support in 2011 when several oarfish washed up on beaches in Japan only some months before the destructive Tōhoku earthquake and tsunami. This catastrophic event, measured 9.0 on the scale and brought widespread destruction and fatalities. This made the belief of the ‘doomsday oarfish’ even stronger.