I would say the ML from https://www.mangago.zone/read-manga/even_though_she_is_a_weak_max_daughter_she_has_taken_a_bet_from_a_shrewd_fianc_e/ is more mature as a child lol
Lmao i agree. Rufus is just on another level
But in a good way!
Facts hahaha
Rufus is such a simp and I like it.
lol there is also Prince Cecil from https://www.mangago.zone/read-manga/jishou_akuyaku_reijou_na_konyakusha_no_kansatsu_kiroku/
No lt sure if the older brother of the MC counts but I would say he's too smart
https://www.mangago.zone/read-manga/the_villainess_is_changing_her_role_to_a_brocon/
（￣へ￣）I just can't imagine a child acting so mature. Maybe he's just too smart? I don't know anymore.