Well from what I know is that in the first season was that she was kidnapped when she was a kid and had many suicidal attempt when she started living with the grandpa and the 2 older brothers.
In the second season which tells us more of what actually. sena our current mc is the real daughter but this group of evil sorcerers who kidnapped her when she was a kid did something to her and her soul got switched with the sena who lived on earth. The father who rescued sena from the group of evil sorcerers when she was a kid noticed something was wrong with her. So he summoned a bunch of priest (not sure on this but he summoned bunch of people) to returned his daughter back but the priest fail to do so and that made the father go mad and that's when they send "sena" to her grandfather. I forgot what happen to sena mother but I did remember that she was searching for her daughter in many different world which she ended up finding her on earth, in the orphan and which she introduced herself as the teacher instead. Sena also learned that the teacher is her real mom when she went to the capital to get permission from her dad for the school. But she learned that the teacher is the mom cause of the picture when the maid gave her a tour and that's when she had a lil talk with her dad of what I say earlier. The dad was happy to have his daughter back cuz she is the real sena who belongs in the world they in right now, as she didn't belong on the earth we know.
But as for the saintes thing there are many of them but it basically just a pure heart girl who can open portals. So as long as the girl can open portals they're consider as saintes. ╮(￣▽￣)╭ so far there is only 2 who they consider as true saint because the first saintes (forgotten her name) she was able to open portal for over 100k soldiers at once. While sena which we still don't know how strong she is but so far it seems like she's stronger only because she can open a portal that was like half across the world which was in the first season where she first open her portal.
But in the ending of the second season. Sena was having a tag of war with the other saintes. She thought she lost her power but it was kind of a tag of war as they were trying to open the portal at the same time which sena uses the door that opens from both end as a reference. So only one saintes can open at once. If both open, it cancel each other out. Which sena didn't know about till later on. Well while she thought she lost her power. A bunch of nasty girls who was on the empress side was claiming that sena was not a saintes as she doesn't wanna open the portal in front of the emperor and many other Noble when asked to do many believed that she was a fake but she ended up being able to open her portal when she got invited by the empress for tea time or something. Well thanks to this tag of war with the other saintes. It proved that sena was stronger than the other saintes as she was finally able to open the portal that the other saintes kept closed.
But I do agreed it's sad that they slowly going away from cooking ever since she went to the capital to get her form sign for the new semester from her dad. Which is what the second half of season two （￣へ￣).
As for the villain. If your talking about the blonde boy who is the first prince. I don't like him but it's mainly cuz of the empress who cancel the engagement of the former saintes and is trying to get sena engaged to him instead of our ML. I just find it funny that they changed the character feeling of the former and current empress' into hating sena cause in the end of first season when sena went to the palace for a whole week. She was in good terms at the end, gaining both former and current empress side but all of a sudden now they on bad terms. Idk why the former and current empress is trying to sabotage our sena at all ┑(￣Д ￣)┍
saw that it updated, and the new chapter i was wondering why it looked funny but turns out the art change YET AGAIN?! just stick with one art style bro. plus the story is just getting more and more confusing like I'm sorry so her past teacher is actually her mom who died and sent her soul into the other world and that she sent her back going with her as a perfection charm, and that there's two Saintes's which is very weird but like I can't tell if one real or both are and plus she stopped cooking which had got me hooked on this and now there's a new villain uhhhhhhhhh it's just too much man.