The plot is contrived to the point of being ridiculous.
The West supplies the princes "equally" with weapons "to prolong the war" to help rebellion of conquered nations. It would never work. Maintaining balance of three sides by equal weapon supply is impossible. Three-way conflict is inherently unstable, princes can make temporary alliances of opportunity, stupid mistakes, bad luck, etc. Supplying princes with weapons makes them stronger relative to rebels though. Supplying the rebels would actually make sense.
Both Wein and Lowa easily see through the plot but imperial princes don't believe her "because she is a girl". Maybe they didn't believe her because she is an enemy in succession war and lies like breathes? Nah, must be the girl thing. Damn chauvinists. Anyway, the equal supply idea is ridiculous so believing it would be dumb.
Lowa's genius plan is to go to Natra so that one of rebellious factions attack the country to capture her and let Natra beat them up. It supposedly will prove to the princes that she was right the whole time. This is retarded in multiple ways.
- The princess is completely useless for rebels. They fight for independence from the empire, why would they need imperial princess? If they try to become the new rulers of the empire it would make this particular faction an enemy of all three princes, all the remaining rebels, Natra and the West. Entire continent basically. If they can deal with all that why would they need the princess? How did they end up under empire in the first place?
- Conquering Natra to capture the princess doesn't make any sense. She can easily escape. Sending troops abroad means significant expenses and losses directly impeding the rebellion. Using small group to covertly capture the princess in transit is much simpler and risk-free.
- If the rebels attack, how exactly it proves the existence of Empire wide plan of rebellion? It is obviously an individual faction action.
- Lowa assumes that Natra will defeat Gairan province even though they have 1 to 8 disadvantage in forces. Wasn't she supposed to be a genius?
- Why would Natra even try? Lowa tries to provoke an unwinnable war for her "friend". Giving her to Gairan is a perfectly moral option. Wein wouldn't do it "because of Ninym" she says - if rebellion is successful it will be a victory for West and West doesn't like Flahms. Wow. Capturing Lowa doesn't mean rebellion wins, she is nobody in Empire's politics. She will be a very minor empire's problem as she was before she came to Natra. Wein can just return her to the princes directly and make them deal with Gairan.
She can fall off a balcony too, accidents do happen. As she astutely notes, "my life means little in the grand scheme of things, peace within the empire must be my prime objective". Well, it works for Natra exactly the same way.
Supporting Lowa, on the other hand, makes her a major pain in the ass for Natra. Like, thousands dead, occupation, end of dynasty, this kind of pain.
- Why would Lowa try to manipulate Wein? The guy is smarter than her, it would never happen. His country is far away, doesn't have any meaningful military power and he is not interested in empire's power struggle. Empire is fractured and full of morons, if she is so damn smart she could manipulate any of multiple factions.
Wein's genius counter move - he writes a letter that Lowa comes to Gairan next. Ok, why would Wein declare Lowa's plans to the third party? Why would the third party believe this letter? That's ridiculous.
Rebels do believe the ridiculous letter. They are even more ridiculous than that, the son of Gairan's boss goes to Natra which they were about to invade assuming the princess would marry him. A voluntary hostage. Why?
So, the next Wein's prediction is "using her hand in marriage as bait she will lure him into telling her about the rebellion". Why would she do it? She already knows about the rebellion and no one believes her.
Ninym asks a surprisingly good question - "even if Natra supports her, what's the difference, we are nobody" only to let genius prince give retarded answer "we can't intervene but if she has our political backing and her grit, put them together and they become something, don't you think?" No, Wein, nobody thinks that. Without power to intervene you political backing is nothing and her grit is another nothing. Put two nothings together and you get nothing. Freaking genius.
It doesn't get any better after that. Lowa supposedly will try to put down the rebellion using retarded son's support and Natra's troops. She has another genius trick in her sleeve to borrow non existent Natra troops which sadly will never be revealed because retarded son is too dumb to breathe. It's a damn shame, she is completely confident in it so it must be really genius this time.
This strange accident makes Lowa give up on her throne ambitions for some weird reason. She doesn't want to rule anymore, now she just wants to crush the rebellion. Hmm, wait, her previous plan wouldn't help her to rule in any way so what exactly she "surrendered"? She doesn't really have any forces of her own, so she wants Wein's help. Naturally Wein will help her, after all she is a good friend who maliciously put Natra at unwinnable war with the empire without achieving anything.
Oh, by the way, they are at war but don't really need to win militarily, they just "want to hear him confess about the rebellion". How would it help them? Both presumably have spies and know enough about the rebellion. Lowa tried to warn brothers, they didn't believe her because "she is a girl", succession opponent and habitual liar. Wein is a foreigner and Lowa's ally. Confession doen't change any of these things.
Rebels can't decide if they want the invasion or not. There was a plan for invasion but Wein's letter prevented it. "Damn you, Wein!" The stupid son died, invasion is a go. "The timing couldn't have been worse." The prince can't fart without completely ruining rebel's plans. That's what makes him a genius.
Author tried to make it complex and interesting. But it is just so dumb. Instead of making MC outsmart the opponents he makes opponents outdumb the MC so that regardless how ridiculous his actions are the victory is inevitable.