so I'm thinking that the Middle daughter either likes the Oldest daughter's Aideor manipulates the Aide for information
They most definitely in love the aide always looks sad then he looks at her or when the mc talked about the marriage.
Σ(  ̄□ ̄||) it always looked like a sneer to me
so I'm thinking that the Middle daughter either
likes the Oldest daughter's Aide
or manipulates the Aide for information