From my read of MTL of WN vol 5 (there may be inaccuracies)
- It was Olivia who was kidnapped because Lelia knows from the third game that Olivia is OP and feared her. Leon rescues her just before being violated.
- It seems that Leon is the one who set the sacred tree on fire. Also Luxion won against Edea by having Creare implanting a virus in Edea.
-Emile dies after becoming one with the sacred tree. Emile was jealous of Serge for hanging around Lelia a lot and seeing Lelia relying on Serge a lot. Emile becomes one with the sacred tree to show that he can protect her and can be relied upon and rampages. Lelia was able to stop Emile's rampage after fusing herself as well. When the rampage ended the tree disappeared and Lelia was fine and there was another sacred tree sapling.
- king = acting chairman Albergue in LN
- Leon really did not interact with Emile and was indifferent about him. He was more surprised that the chairman who was suppose to the last boss was not the last boss but it was Emile who became the last boss.
- The all the nobles did not die, some did in the fighting. That is why many of the nobles hated Serge for picking a fight with Leon. The nobles tried to get help from Leon on reconstruction by making him a part of the 6 nobles. Which Leon refused.
- Lelia becomes the priestess of the sacred tree left behind by Emile. So there seems to be two sacred tree saplings, one found in dungeon and other created by Emile.
- Eric is the WN version of Loic. Lelia did not know about the bad end (Noelle being killed by Loic) because she avoided playing that route in past life.
- Leon "bought" Noelle by offering the magic stones he got from Luxion when it plundered the republic's ships when causing chaos. Leon did so because he and Marie saw the abuse by Eric on Noelle.
- Eric later attacks Marie's mansion to get Noelle back and after being subdued, Marie admonishes Eric about his behavior. Eric becomes awed by Marie and wanted to serve under her as her little brother.
- At the end, Eric tried to follow Marie to the kingdom but Marie stopped him telling him to not abandon his family. She tells him he is better than the other 5 and said that in the future she will visit him as much as he wants when he becomes a great man. Cara and Kyle was a bit disappointed because Eric was on the helping side rather than the parasite side.
- It was Leon's father who came complains to Leon that the situation at home is bad because mother thinks the father cheated and Marie is father's biological child.
- Leon gets promoted to marquis because the king wants to harass him for giving him more work to do by causing chaos in republic. The king also puts 4 of the Marie's guys as his retainers to harass him even further, Leon needed some retainers as marquis. Julius cannot be a retainer as he is the prince, although Julius felt left out and stated he wanted to become a retainer.
- Excerpt (korean translation I can read a little)
On my legs, Marie, Cara and Kyle latched on to me.
Leon: "You..., You all just what are you scheming."
Marie: "I'll never let you go. Brother, take care of me forever!"
Cara:"Count, no Marquis! I'll follow you forever with Ms.Marie!"
Kyle:"If we let go of Marquis, will we not be in big trouble. Let's work hard together!"
You all..., Are you all trying to pull me to your side?
Leon:"Let, let me go! I hate taking care of you all! I will not do it!"
Marie will not leave my legs.
Putting strength into it Marie latched on my legs. I can feel the commitment.
Marie:"Brother--- we're together forever."
Marie, who latched on to my leg, looked up at me as she smiled --- it felt like a horror movie.
Marie's smile was frightening
In an instant I felt cold and felt cold sweat on my back.
Leon:"NOOOOO!! Someone help me!"
Just what did I do to deserve this.
Just what did I do to deserve this penalty game like situation?!
Anyone is fine, just explain it to me!
-Leon does not study abroad again, he stays in the academy in the kingdom and the kingdom is not invaded during this volume.