Soul Gluttony

is a Japanese light novel series written by Kazuki Izumitani, with illustrations by Shugasuku. The series began publication on March 10, 2015 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
Alisa Kurosu, the girl of "Ouroboros" who was destined to fight a monster called soul for the immortal king behind the scenes of history. By meeting such a girlfriend, the peaceful daily life of a high school student, Fushigami, transforms into something unusual.

He became the 100th Immortal King, and his extraordinary ability "Gratney" is an immortal and predatory ability that bears the name of "Gluttony", and has the restriction that he must continue to eat the soul of Seoul. So to speak, it is a "curse". Maru decides to cooperate with Alisa in order to fight the vicious soul with her power.