I wonder if something happened to the author. The webnovel ends at the exact same point, and they have posted nothing since the latest chapter, three years ago.
On the activity reports on Narou, there's a suggestion, they say that this is the end of part one (so yeah, it sort of is a 'season 1 ending') and that there would be a parallel story for Leandra coming out (showing her story from when they met as children up until the engagement.) But I can find no evidence for that ever coming out.
Dunno. Maybe they gave up? But the manga and the serialized digital chapters are available on amazon.jp up until this same point. They must have done those after the webnovel was done, since their publication is much more recent.
Alternative explanation would be, they are still working on the parallel story and want to have that prepared before heading to "season 2" of the main story.