The Great Disaster of Sagami Bay (相模湾岸大災厄 Sagami-wangan Dai-saiyaku?) was the worst Aradama-related tragedy in history which happened on September 26, 1998. The incident occurred on the coast of Sagami Bay that led to large amounts of Noro being leaked into the sea, which formed into the largest Aradama ever observed. The Aradama landed on the coast and headed north, causing large-scale damage to the city of Fujisawa, which resulted in over 3000 casualties. Through cooperation of the SRRS and the Self-Defense Force, the Aradama was driven to Enoshima. Thanks to the efforts of the select few elites of the SRRS, it was successfully subjugated. Following the event, the aforementioned six elites were labeled heroes.

The ones who vanquished the Great Aradama were Yukari Origami, Ema Kagamishima, Iroha Yoshino, Yukina Sagami, Sana Arami, and Yuzuki Fushimi.

It is revealed that the real heroes of the event is Kagari Juujou and Minato Etou, but they failed to destroy the Great Aradama entirely, a part of it survive and possessing Yukari Origami.

Also according to Richard Friedman, this disaster cause by the action of human trying to gathering Noro in an oil tanker, and bring it to U.S oversea.