I'm at chapter 22 at this moment: 21 Oct 2019. I might edit this comment again.
I really enjoy this series: It's funny, hectic and straight-faced crazy. The contrast personalities between the two sisters are hilarious and created plenty of hilarities thus far.
By intention, the older sister "the ally of justice" unintentionally. She is seen to have indirectly influenced people to improve and strive to be better or even change their mindset about certain issues in life (i.e. overworking, patience, manners, social behaviours, etc.); Afterward their lives change 180 degree around and most of the time become better.
The little sister also benefits from these although she endured hells from her older sister (from our reader perspectives, the older sister is self-center and cares about no one, even her husband and child, but herself; yet always somehow extremely fortunate and gets everything she demands).
The PROBLEMS arise when some of these indirect "s", "encouragements" with some being "insults" and downright "bad manners" and "insensitive behaviours" are deeply ingrained as perceived "acceptable behaviours" in society (here Japan, might apply to many other Asian countries).
Personally, these problems are dated and backward and many are contractions and deeply rooted in a patriarch mindset with little progression for women developments.
The moment I realised these outdated ideas - being pushed by the older sister character and author - are no longer tolerable is in chapter 22: a new mother is having absolute hell by-herself trying to take care of her newborn daughter and home without any helping from anyone (be reminded that the older sister stays at her parents home and get her parents and sister to take care of her own baby) while her husband works. By no mean should I weight who is better, who gets it fair, because it's due to personal circumstances. And if you've ever taken care of a newborn baby by yourself or witnessed/ed such guardians everyday, would you have the empathy towards them.
Here, what the new mother needs is sympathy. Instead she got concerning eyes from her circle of friends and downright scorns - even indirect abusive comments - from a stranger/the ally of justice/the older sister.
Then, with those little words of confinement and domestication that entrapped the Japanese/Eastern ideals of a mother and woman, she returns home, fixes herself miraculously by some means no one knows: the house is cleaned, the meals are great, and she suddenly wanted another baby!
I feel absolutely sorry and horrified at this point.
At the same time, I understand that this is way back (2000s circa). Still, I can't shake off how much of a sexist and bully this manga is.
I hope this might be sarcasm or a sort of social commentary work. Or at least provide some insights and internal contexts or personal back stories so we can shed some lights into such an antagonistic character of the older sister. Maybe that would explain her view of the world, and make senses of the person she is to make her less terrible.