Shiou no Kikan: Moto Yuusha no Ore, Jibun ga Soshiki Shita Chuuni Himitsu Kessha o Tomeru tame ni Futatabi Isekai ni Shoukan Sareteshimau

Synopsis:

"How can my former self get so delighted doing all those embarrassing things!?" Hizaki Shiou was called to another world to save it during his third year of middle school. He was dragged back to the present after vanquishing the Demon King. Three years later, he is called to the other world once more, this time to put an end to the "Helheim" secret society's rampage. During his chuunibyou phase, when he referred to himself as the "Corpse King"—a dark past too embarrassing to recall—he allegedly formed that group. It appears that someone is using the name "Helheim" fraudulently and damaging its reputation. The Corpse King reunites with his old subordinates, the "Hakkai," who had made Helheim the strongest it has ever been, in order to solve this riddle and clear the organization's name. He starts acting in the other world once more while suffering from his terrible history. The Steel City of Gagiul is their first destination; they must save both the starving city and the distressed daughter of the pale-looking count.Helheim, I am leaving."