The person from our world is called the Beneficiary and the 'host' of that world is someone who has called for one, albeit sometimes unknowingly. The 'host' soul/personality doesn't disappear either, but rather they merged together. (From Rosalia + Rin = Rosarin)
I especially like this since it wasn't a dead person from our world typically taking over a child's life, but rather a wish granted by both parties.
The family also realised that their kid has changed, becoming a Beneficiary, right from the very beginning. So no "gotta keep this a secret" schtick. They are very observant and supportive too, compared to the typical cast in the kinda stories.
Firstly, many thanks to the translators, as the original author is apparently very bad at punctuation. Without them, this would be illegible.
Things take on the typical isekai speel here with a chapter of floundering, another of exploring the setting, then gaining a HAX item/skill, meeting a beautiful female and then to civilization we go!
For some reason, MC wants to become an Adventurer?
Then typical exploring the shops, beginner quest stuff happens.
The also-reincarnated bf is an idiot, who doesn't even realise he's an idiot for proposing to a modern woman that she should be his 2nd wife.
The first "friend" character we see is selfish, petty, and extremely 2D. Techniques of any kind back then were usually kept secret as they are the key to success. So you don't lightly ask for one.
Except, let's lift the curse with the power of LOVE!
Surprisingly, the MC isn't forced to have s*x with him to do this, a mutual love confession worked.
This country has a French-ish feel. The King is called Rousseau. There's a movement for equality going on. The Otome game is called "Revolution".
Luckily no-one was guillotine'd but it was a close call.
Rejoice, for there is a Good End!
Especially when you realise that the reason Fredericka went away quickly from the ball in the beginning wasn't because she was heartbroken, but embarrassed and panicked because her old sidestring panties have come undone and she's a minute away from losing them.
Which she did.
And then someone picked up.