The mc and her army is considerably weaker here compared to the WN/LN, since they able to curbstomp most of the opponent. The major opponent they have is the empire, and the country across the continent where the the twin tailed girl that appear in the end of the chapter, She's also the last boss of the WN too.
her main hero army, beside serignan is one of the elf girl who has been transformed into one of her swarm, but still keep her monster lady appearance, therefore another cutie for the army
The main theme for the mc character growth is redemption, since the main focus of the story is solving the mystery why she appear in the world and what is that world exactly. Thx to this mission of her, she's become not so unhinged to the swarm and able to think independently, this also affect the swarm which become a more peaceful and not as brutal as before
One of the most important character that has not appear in the manga is the loli goddess girl, which basically the big good of the story and the rival for the twin-tailed girl. Perhaps one of the reason MC regained her sense in the upcoming story is due to her guidance.
In the end, its revealed that the world they live is actually some kind of hell created by the twin tailed girl to punish those has sinned in the real world. Maybe we can assume that there's another reincarnator in that world too tough im not sure about it since i forgot
In this case, the MC biggest sin is killing her sickly parent by turning off their life support and then killing herself due to the guilt of this act. She need to defeat the Twin Tailed Army in the other continent to finally have her chance at redemption. She finally able to defeat her at the final epic war, i do remember she use some kind of giant-sized juggernaut insect to act as a bait while laying down the siege and finally stab the Twin Tailed girl using some kind of sword that can only be wield by reincarnator.
She finally able to get her redemption and move on to the afterlife, leaving her army behind. I remember that she want to choose Serignan as the new leader of the swarm, but she refuse and say only the MC can be their leader. In the end, the remnant of the army live co-exist peacefully with the other races, while they leave the MC throne empty
Well, thats what i remember mostly tough