Tsumi no Kyojin to Gindokei no Aria (Volume)

is the first volume of the Tsumi no Kyojin to Gindokei no Aria light novel series, written by Minato Ishikawa and Illustrated by Kashii. It was released under the Dengeki Bunko Imprint in October 2018.

Synopsis
The legendary giant "Giant", also known as a natural disaster. The hero who aims at the magic stone "Giant of Time" that is in the heart is taken into the body of the giant from a momentary ski. The awakened hero lost his memory and was no longer protected by his spirits. What appeared there was Aria, a girl with a silver clock, with a stake piercing her chest and not knowing when she was here. The two head to the heart of the giant to find the hero's memory and exit. While advancing through a dungeon full of traps, when the hero opened the door to the next room, suddenly someone pushed his back and fell head-on into the abyss. "I'm sorry, but that's it. Goodbye, hero--"

(source: Dengeki Bunko Official Website - Translated)