The only way I can read this manga without getting completely pissed off at Kamiya's power level is to reimagine it as a story about the battle between two gods--Metron and Kamiya. You see, Metron is the god of another world who unthinkingly bestowed the Magic Creation and Super-Growth abilities onto what used to be a normal human. Kamiya is a nascent god who lives on earth and just wants to sleep all day. He attracts female admirers, who would love the honor of bearing his demigod children if he would only look their way. So far these admirers include his stepsister Karen, his androphobic classmate Kamaishi, and the angelic being Lina.
But honestly, reimagining the story this way doesn't much help since it just brings up cosmological questions which the manga has no intention of answering. Like what are the rules that govern what gods can and can't do (since Metron is clearly disallowed from certain actions) and is it the upper gods that enforce these rules? What's the nature of the upper gods and are there upper upper gods above them? (Is it turtles all the way down?) Why does Metron even care about Kamiya at this point? Can't he just bestow the Super-Growth ability on the 39 other classmates who actually did get summoned to his world? It really, really just feels like the plotline is revolving around Kamiya--and Metron is concerned with Kamiya--specifically because that's what needs to happen for him to be a proper protagonist. It's so obviously contrived.
The first two chapters were okay. Then in chapter three, fantasy monsters started appearing on earth and it was like "This is dumb. If the entire premise of your story is he's remaining on earth, then have him deal with earth threats (like the terrorists from the first two chapters)." Then when Lina tries to force him to come to Metron's world, it did create some interesting tension where he had to fight to stay in this world. But then we realize that even if he was summoned to that other world, he could just create magic that allowed him to teleport back to earth, which destroyed all the tension and made everything seem pointless. His power level makes everything seem pointless.
[Reviewed at chapter 19]
Spoilers there is incest. It’s starts with a growing relationship between classmates then switches to the brother sister relationship then to Harem while still giving the side story of the other world. When they’re explaining their no blood relationship, they are just distant relatives and the MC was adopted by my parents. The girl knows this and still wants to be with her step-brother/blood-relative . Besides that the story really is your basic cliché teen storytelling with the MC becomes a wizard in the real world.