Ayuhara Yorunami wa Yoku Nureru

is a Japanese light novel series written by Hazuki Minase, with illustrations by Eiri Shirai. The series began publication on September 10, 2013 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
Yohei Nagisa, a boy who drowned in the pool at midnight, noticed that the whole area was on the roof of the school where the sea sank.

In that world, I met Ayuhara Yanami, a girl with a jellyfish-like atmosphere floating in the sea. She was an "Undine Warrior" who wore a combat magic costume "Cloak" that could gain more power the more she got wet, and fought against monsters ...