you have to check the raw WN for this, especially the interlude part after the second part finishes, as far i know, the interlude is never translated, this give some POV from anne, one of the maid who betrayed mc and nina, and also POV from the empire girl who assist stupid wilhelm (which shows she killed stupid wilhelm in the end)
https://ncode.syosetu.com/n5873ib/122/
https://ncode.syosetu.com/n5873ib/123/
https://ncode.syosetu.com/n5873ib/124/
if you read the raw WN, you can see the author intended to continue the story into 3rd arc where, they finally face the empire led by empress anastasia, the leader of the country who is going to annex the mc country
it also give some plot where the 2nd prince intend to freed the 3rd prince after that doofus got confined in the tower
but alas, there's no continuation on the WN part too, so we never know how the 3rd arc will play out