The Return of the Corpse King

"How could my past self get so excited doing all those embarrassing things!?" When he was in the third year of middle school, Shiou Hizaki was summoned to another world to save it. After defeating the Demon King, he was forcibly returned back to the present day. Yet another three years later, he is summoned to the other world once again, this time to stop the rampage of the secret society "Helheim." That organization was supposedly actually the one that he had founded during his chuunibyou pha...