Haru really did love her

Groomer by who?

She was a student when she was sold off in marriage to Tougo's family. Whether willing or not, Tougo, as well as both families groomed a young girl in school for marriage.

I don't think groomed is the right word to use. Grooming is using controlling/manipulative tactics to get someone to do something. What did they do to haru to force her into marriage?

From the UK Met Police, "Grooming is when a person builds a relationship with a child, young person or an adult who's at risk so they can abuse them and manipulate them into doing things." Here, the end goal was to marry her as a respectable wife. The qualities that recommended her for this was simply knowing how to cook and loving children.
Re: Haru being forced to marry. A child cannot consent. A child absolutely cannot consent when the other person in question is an adult. She's literally in a school uniform when the marriage interview takes place, with her father at her side. In that household, where the sisters could only depend on each other, do you think she could have spoken against her father's implicit agreement that marriage between her and an adult was okay? Did she even have enough maturity to know about the issues with age gaps and power imbalance?

Furthermore, even if she did want to marry Tougo, so what? A suave, professional, handsome gentleman comes in and proposes and a child imagines she's in love. Does that make marriage between them okay? She didn't even know her options. She was escorted on dates with an older man. He acclimatized her to a more adult dating life, while she lacked maturity. She was anxious until she saw how handsome she was. If Tougo was ugly, would she still have fallen in love? Who knows. She hadn't even developed her true tastes yet. My taste in food, literature and clothes have changed dramatically since I was 16. She never got the chance because she already had the image of a finacè in her head. In many cultures, girls are married as children to older men. They may grow to even love them in time. But was the deprivation pf their autonomy right? No.

I think the unbalanced power dynamic plays a large role in the story ( the obvious one is class/wealth, but also the younger sister’s jealousy of the older I think also stems from the fact that she is closer to Tougo’s age… she says she wants to be more mature) but also I wouldn’t use the word grooming. It has very specific, criminal implications which I don’t think can be applied in this case… part of the whole point of the story is that tougo is also a victim of his family. He isn’t really shown doing anything towards her (they literally go to the library for dates ) that isn’t just common courtesy, and seems obviously very disengaged and passive… I wouldn’t describe his presentation towards her as “sauve” lol. He is in college while she is in high school, which yes, is a large gap in life experience, but also he is still a dependent of his family… his arc in the story is his full independence, maybe his true adulthood. there r definitely troubling dynamics at play here, but there r other ways to describe them than “grooming,” which also seems to place the responsibility on tougo which i think is not quite right

I'll argue it is criminal. Just because nothing sexual took place doesn't mean it isn't grooming. There are plenty of cases of platonic grooming too.
And while Tougo's dependence on his family is sad, he was an adult who had quite a strong educational background. He had the strength and the ability to rebel when it involved the woman he loved, but not for the child he was engaged to?
I'm from a developing country. I have seen cases of adult men being "engaged" to girls who aren't yet 18. The engagements last long and the marriage happens after they turn 18, perhaps even after getting a Bachelor's degree, because these men want educated wives. Our culture allows for the elders in the family to dictate a lot. And yet I will say that the men who aren't interested in marrying a child and have no sexual interests jn their young wives are just as much as at fault as their parents and the "bride's" parents. They chose to take away a child's potential growth and experience for comfort in their own lives. This comfort is the connection to their families, wealth, status, etc. They give up nothing and stay somewhat uncomfortable while a girl is robbed of growth.

Tougo is not a purely "good" character. He has flaws and it adds to the story to recognise those flaws. It is easy to see Natsumi's grey zones in the story, but we must understand that Tougo also was party to the crime, even though Haru herself, as the child, was not aware of it.

Well, that’s ok I guess. All I’m trying to say is that ur version seems to be quite a black and white view of the story, which I think deserves & encourages a bit more nuance than that. We can (& I would agree) think that tougo as a representative of his family has wronged haru, without taking the extra step that he has therefore committed a grave crime & is a bad person (& here I’m assuming u mean in a moral, human sense rather than a legal sense). We have no idea what kind of person haru would have been — part of the point & tragedy of the story is that she has been robbed of this, not ultimately by tougo, but by her illness.

I also think this is not "grooming", Haru was just caught in an arranged marriage. Luckily Haru liked Tougo. Anyway, based on my understanding with the story, Haru didn't know she will have an arranged marriage until the time Tougo's mother wants them to connect with Haru's family and also she was chosen at that time because her character was more acceptable than the older sister. So in my opinion, no grooming was done