@Hadski
@AbyssalMonkey
@Tcof  
chapter 12: 
17 years ago, chateau was a little girl
https://mangadex.org/chapter/363848/5
https://mangadex.org/chapter/363848/6
https://mangadex.org/chapter/363848/7
chapter 29: (also 17 years ago) male lead is a teenager  so chapter 3's estimate of ML's age: 
32 seems accurate.
https://mangadex.org/chapter/625721/1 
https://mangadex.org/chapter/625721/3
chapter 30.5: little chateau's official age was stated to be 4  
https://mangadex.org/chapter/649584/12
so chateau is 4 + 17 =
 21 officially