
Even in the last century of American history, there was a picture of a 30 year old man with his 9 year old wife in my HS txtbook. The caption was that he gave her a doll for her 9th bday, so they got married before then. In modern day, I've subbed in junior HS and had to report 12 year old children having sex with each other.
Important note, I think that Sumire has shown that she is ok with being sexually active and that between the 2 it was consensual.

just because its fiction doesn't mean it can't make people uncomfortable. this may be all fine in their world but irl [in some countries] it's not and "oh its fiction so let's drop all our morals and pretend we love the things we don't approve of personally" doesn't quite happen. which is why things like age, rape, and so on make people uncomfortable. just because its fiction doesn't make it suddenly ok to those who feels strongly about the subjects. romanticizing problematic things is a problem in itself since they can set an example to impressionable minds.
it is, however, not good to bash or bully the author over them
it is important to separate fiction from reality but that doesn't mean they have to approve just because its fiction

I don't think anyone are trying to make people forcefully approve something. It's fine if you're not okay with it. I have my own set of boundaries that I'm not okay with and actively avoid to read in a manga.
However, wasting time complaining about it in the reply section is quite irritating. Especially if it keep repeating the same point of complaint with the others.
Judging by the comments, lots of people forgot this is a story, and not reality. Those that judge stories, by their realities, may find a few things hard to swallow.
And let me just say this once . . . . if I had a green thumb, that plant would be so cool to have around!!!! I would hope it's smart enough to take care of itself, as it would not last long under my care (killed a cactus previously).