I did this particular drawing while participating in a Drawlloween prompt challenge. I had gotten fatigued from constantly drawing spooky stuff (hard to believe but it happens) and had a prompt to draw a Yokai. I did some digging around and read a little about these ladies.
Basically Umidebito reside in the coastal areas of Japan. They are sometimes presented with fish tails like western mermaids, sometimes as ghostly sprites, but mostly as beautiful women in shells. Unlike the sirens of western lore, they are not known to lure sailors onto the rocks and their destruction, but are considered to be Oracles of a sort. They are even positive Oracles and typically bring good tidings.
At any rate, I enjoyed the break from darkness and drawing this wonder of the sea. Ukiyo E style drawing done in Pen and Ink and colored with wc brush pens on bristol