Yea, i see... I read a bit of what you are saying, and it sound retarded to me...
Asuna is 15 years old, which is the same with most of the students there. we dont know details, but we know the year they are in and thus they should be 15!
Also note that Anya said the same thing when she was comparing breasts :P
And it makes sense, she was not created in any way. She was just a princess, thus she has that power(probably bestowed upon her), but due to the power she was used and mistreated!
First off: I will leave the when Negi was conceived part out because since we know Nagi is still alive, it could have happened even after Nagi was presumed dead, which is when i think it happened, since he dissapeared 10 years ago and Negi is 10 years old.
(Actually we know Negi is 9 years old, so we know he was conceived after Nagi supposedly died) (read chapter 3 for proof that Negi is actualy 9)
Some Facts:
- In the flashbacks we see Asuna looking young, but we dont know age.
- When Negi was saved, he was 4 years old. Asuna was 9.
- Negi now is 10, Asuna is 15.
- People think Nagi died 10 years ago. Asuna was 5 years old at the time.
- When Nagi saved Asuna, she must have been 5 years old at most, that is because when Nagi saves her he gives his name to the people there, thus he has not "disappeared" yet.
- We know that Nagi is traveling with his party, but in no way do we know that he is assumed to have "disappeared at the time!"
What from the above does not makes sense and people are talking about growth problems? Tell me and i will be happy to solve it for you!
These is no time-machine involved, or a test tube. She is a normal human (well you know what i mean by normal)