Undesired Result
For Shimizu Yukitoshi, to be summoned to a different world was the dream he yearned for. Because he knew that was impossible, every day he was dreaming by a reading book in his hand or web novels. In his dream, he saved a lot of worlds, though he didn't know if he went towards the Happy End with the heroines. Inside Shimizu's room, the walls couldn't be seen as they were buried by posters of beautiful girls, and inside the glass rack at one of the walls were his favorite beautiful girl figures with improper poses lined up in such a cramped place. His bookshelf was filled with manga, light novels, thin books, and eroges, while the ones that couldn't be put there were all over the room as they made towers.
That's right, Shimizu Yukitoshi was a genuine otaku. However, there's no one among the classmates who knew that fact. That's because Shimizu himself thoroughly hid it. There was no need to talk about his reasons. He had seen the classmates' attitude towards Hajime, that's why there was no way he could become an open otaku.
Inside class, it could be said he was just a mob character by those who knew him well. There was no one he was especially close to, and he always quietly read a book in his seat. If he was talked to, he would give the minimum answer in a small mutter. To begin with, he kept the quiet attitude because he was bullied in junior high school. Maybe because it was the natural flow, he became a truant and stayed inside his own room every day, and he inevitable tried to create books and games to kill time. Even though his parents always worried about him, he brought otaku goods into his room every day which made his big and little brother annoyed. They even showed that in their attitudes and words, which made Shimizu feel that the comforting house became worse, the so-called losing his place to stay. With such a gloomy environment, Shimizu thought of doing devious things to others inside his mind without letting it out on the surface. Thus he became more and more devoted into delusions and book creation.
Because he was like that, when he understood the summoning to a different world was the truth, his mind's state was as if shouting, "Here it come--!!". Even at the time Aiko protested fiercely against Ishtar, or when Kouki passionately decided to help humanity win and return to their original world, inside Shimizu's head were only the delusions of the real him doing spectacular things in this different world. He was elated because the delusions he thought as impossible had become truth, and the pattern of being summoned to a different world where the protagonist was being unreasonably demanded was driven away from his mind.
Thus it actually became just as he expected, there was a conflict in this different world life for real. First, Shimizu certainly kept a certain cheat-like spec as a secret, but that was the same thing for the other classmates. Furthermore, Kouki was the "hero," not him and maybe because of that the women only kept coming near Kouki, and it became the saying that "he was just one of the many additional people." With this, nothing changed from the time he was in Japan. Though his wish was fulfilled, the reality that didn't become just like he hoped for made Shimizu increase his deviousness, and his dissatisfaction was increasing in his mind.