1. He transported close to a sage's house, taking in all his (extremely high quality) knowledge from there. Getting all the slimes to help reading is too much of a cheat tho LoL.
2. His absurd MP and HP. On top of being the main reason he wins everytime, his MP allows him to tame too much slimes from the beginning, which helps him in a lot of situations.
3. His almost nonexistent common sense of that world. Because he doesn't know the basics, he is not caged by limitations. For example, he tamed slimes because he doesn't discriminate a weak-looking monster. He reads through the slimes. He does magic through slimes. He doesn't think those are impossible, thus he is able to do those things.
Of course, the slimes themselves are actually such a cheat monster. But normal people doesn't even think of doing the things he did because of reason 2 and 3.
Just my headcanon though.
Honestly Yuuji is too OP for that world because:
1. He transported close to a sage's house, taking in all his (extremely high quality) knowledge from there. Getting all the slimes to help reading is too much of a cheat tho LoL.
2. His absurd MP and HP. On top of being the main reason he wins everytime, his MP allows him to tame too much slimes from the beginning, which helps him in a lot of situations.
3. His almost nonexistent common sense of that world. Because he doesn't know the basics, he is not caged by limitations. For example, he tamed slimes because he doesn't discriminate a weak-looking monster. He reads through the slimes. He does magic through slimes. He doesn't think those are impossible, thus he is able to do those things.
Of course, the slimes themselves are actually such a cheat monster. But normal people doesn't even think of doing the things he did because of reason 2 and 3.