The Demon King Always Thinks I’m Secretly In Love With Him - Chapter 7

What does it feel like when you have a best-selling detective fiction author for a boyfriend?

Whenever you offend him, he would look at you disdainfully, “A character molded after you could only ever appear in my novel as a deceased victim.”

Whenever you seriously offend him, he would threaten you, “The very next victim who dies in my novel would be named after you.”

Whenever you seriously, seriously offend him, he would add on to the previous threats, “Furthermore, the victim would have died at the hands of an extremely perverse and twisted serial killer, and would have suffered an extremely painful and terrible death.”

But, by a stroke of coincidence, if you happen to be this best-selling author’s editor, he need not resort to the above mentioned tactics. In fact, all he has to do is one, single thing –
-Delay the submission of his draft.

- Description from Novelupdates

Based on the popular Vocaloid series, by HoneyWorks, called “Kokuhoku Yokou Renshuu (Confession Rehearsal)“:

Natsuki, a third-year at Sakuragaoka High School, who holds unrequited feelings for her childhood friend, Yuu, who’s in the Film Club. However, instead of being honest about her feelings, she makes him be her confession “rehearsal” partner. Unable to say her true feelings, things start to get complicated when Miou and Akari, who are also in the Art Club, get involved! Will she ever be able to confess for real!?

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.

Traveling through the fantasy world, becoming the descendant of the immortal family in the fairyland, born with a Chaos Physique, accompanied by a piece of Immortal Bone and a Primordial Seal.Starting with the Chaos Physique, he pushed forward all the way to be invincible.There are thousands of geniuses in the world, and they all have to bow their heads when they see me.