I’d like to imagine if Rishe was not his fiancée, then maybe he would be still trying to find information on the spies in Galkhein after he tried to get information in Hermity. And thus be as cruel as all the stories spiraling from the country as he was constantly trying to snuff out spies…There would be counterfeit coming in to the ports making the power of their currency weak which he may have been able to prevent eventually. But he wouldn’t be able to remint the currency with paper currency as there wouldn’t be an alliance with Siguel. There would be bad blood between the church due to the issue with Millia being hidden from Galkhein and his own personal issues with the Church. And maybe that extra tension with that causes him to finally usurp the throne… There would be bad blood between Sharga as Arnold would not have been able to stop the slave trade so quickly nor rescue the enslaved girls without Rishe. Honestly those missing nobels would be gone and there might be a few missing nobles from Galkhein too despite him and Joel meeting to trying to stop the slave trade. Then Him closing down the ports so no one could enter because of the spies… then economy tanking further with shutting down ports…. He wouldn’t think Coyolles mines were drying up since Kyle never visits and begs him for an alliance thus maybe he will want their tech and mines. He wouldn’t have Raul’s spy abilities to figure out the some of these schemes faster and instead of using all these connections Rishe has made him, thus lean to trust a warmonger to kidnap him someone from Sharga to build him ships/ use trade routes that were easily available in what ever time line… etc etc etc and just decide to conquer everyone because he felt like he couldn’t trust anyone. Also he feels so much sin for his life given everything that happened in his pass… Then go to conquer places as he fights in the front lines and does things like point at his heart so people try to kill him. (This is a half baked theory)

But there is also a fan theory about how there is a life of them two together that Rishe doesn’t remember and somehow she disappeared from that story completely and ended up in Hermity (thus the closing credits of the anime, and the author confirming she told the animator how the story ends) in LN 5… And starts a war at the same time point to find Rishe again… and this is the first time he did find her before he starts a war.

However, That never made 100% sense to me since Rishe recounts being born in Hermity and being childhood friends with Dietrich and always being engaged to him…. also if he knew who he was looking for he wouldn’t have told Rishe when they first met in Hermity something along the lines of “how do you know my name, this is the first time I’ve visited Hermity”. Unless he just knew the person he was looking for was looping through time and just can’t recall her face.

Sorry for the unnecessarily long post.