Tokyo—a bustling city brimming with technology and culture—is the heart of Japan. It is the center of the country's government, acts as its economic hub, and attracts thousands of people from tourists to businessmen worldwide. All seems well, until a terrifying 8.1 magnitude earthquake brings the city to its knees. The calamitous event destroys schools, hospitals, and other critical national infrastructure—leaving hundreds dead and thousands homeless without food or water. Jin Mishima is a 21-year-old college senior who is caught up in the earthquake. Accompanying him is his old friend, the outlandish gothic lolita Nanako Okano. Together, the two must survive the harsh social and practical realities brought about by the earthquake—in a Tokyo where crime is rife, no person is safe, and only the combined effort of the survivors can end the anarchy of the city's crumbling society. [Written by MAL Rewrite]

Kanojo wo Mamoru 51 no Houhou was licensed in English as 51 Ways to Save Her by CMX Manga, but was never published due to the publisher going defunct. The series was published in French by Panini France from February 11, 2009 to August 25, 2010. It has been licensed in Spanish by Ponent Mon.