Supreme Casanova: Ultimate Harem System - Chapter 31: Going To Class.

Attribute Classification: Overhead/Western Magic/Strong Attack/Sweet

- Description from novelbuddy

This is a century glittering with the brilliance of human civilization, a world where steam engines, magic, and demi-humans coexist, a chapter of complaints committed due to exploration.'Red Dragon Queen rises first, annihilating all human affairs with her wrathful flames.''The mysterious child of the sea will raise great waves to erase the sins of humanity.''The god of the skies will leave no refuge for the remnants, nowhere to belong.''The immortal witch composes epitaphs for them with her magic.''And I, will write a new chapter for this world'... ...... ...Years later, Fisher, who has received the apocalyptic prophecy and the miraculous tool called the Demi-Human Girls' Completion Manual, wishes to be recognized as a pioneer in demi-human academia, a savior of human civilization, a dove of peace, and a messiah.Instead of being the person who is torn apart with the firewood knife, and the savior divided into pieces.

An alien race invaded the Earth on June 6, 2128. At the midst of this war, many nations allied with the alien threat and the war nearly wiped out the rebelling humans of the planet. At the edge of mankind's survival, the United Nations Army launched its forces to eliminate the immediate stellar threats that loomed over Earth.

General Seeker Carlean, commander and leader of the mission, risked and gave his life to destroy the immediate stellar threat. The battle was won though Earth lay in ruins. Perhaps mankind will live to see a few years of peace before the alien threat returns to wipe out their existence.

At the immediate aftermath of the stellar battle, the fallen Seeker Carlean awakens and finds himself at aged 17, living the peaceful life he lived 16 years before he died.

So begins a new game in the battle for humanity's survival.

A girl who calls herself a demon appeared before a timid student named Fumio Kijima. The girl claims to be a campaign girl from the demon world and she gives him the ability to “summon a room” from nothing but thin air.

At first he doesn’t abuse his power and uses it as a convenient ability in his every day life. But one day he is bullied by his classmates under a false pretext and is made to suffer. In the past he would have wallowed in misery and cried himself to sleep, but now he had a power to call upon.

“I will make them regret it!”

Using his powers to summon his “room”, he begins his era of confinement and brainwashing to achieve his goals.