I'm the Ex-Girlfriend of a Soldier
Sei Hiroin ni Tensei Shita Tokken de, Oshi (Kuzu Otoko) o Kokuo ni Shimasu
This is such a cliche it borders on boring. The plot can be seen a thousand miles away. The villains not only discuss their plans with their underlings in the middle of a ball (not on a locked chamber, not on a hidden place - but literally on a huge open spot were anyone can pass by), they also give a step by step explanation on what they did and what they plan to do and how the MC ruined their plans. The MCs worries are... very superficial. Well, sometimes she worries about how the ML will work as a king. But that's about it. No plans, no thinking. If you want to jump headfirst to immerse yourself on this story... be careful because it is shallow as a puddle. I'd give the MC a mental age of 6. Nevermind she was a grown working woman before the reincarnation.
The Scholar's Reincarnation