The idea of a strategy isekai is great, but this novel kind of just butchers it. The MC's starting abilities allow him to one-shot (and potentially capture) essentially any single person in a battle, and also fight on par with the best in the continent for 30 minutes. That's insane. That in combination with the unbelievable power disparity between the weak and the strong (1 person can easily take on 500+ people) means that tactics, which seems to be what the series is focusing on, are more or less irrelevant unless it's along the lines of poisoning the enemy commander as anything less won't do anything to bring down these super-humans. Also he legitimately gets a billion dollars right off the bat. Are you kidding me?
Additionally, the leveling system is bad. Like 1990s RPG bad. When the MC levels up he gets points, with which he can increase his "Martial" by 1 (battle stat), get a random Attack/Defense/"Special" skill, or upgrade an item. There is just nothing to this leveling system. Also, the battles are essentially entirely determined by this Martial skill (there is essentially an auto-attack system), probably because the author wasn't confident in writing sword-fights, so there isn't much strategy to the battles themselves
Finally, the characters: they suck. Really no two ways about this one, every character is pretty much paper thin, shows no actual character, and obviously exists solely to interact with the MC. This is an issue that the series could improve on much more easily than the rest of what I am criticizing, but I sincerely doubt that will happen, and honestly I'm not going to be sticking around to find out.
P.S.: Why name two kingdoms Runan and Rozen, and two characters Ronan and Runan? They're so similar.