Ok, so... I want to preface this by saying I have zero translation skills. This is the opinion of a lowly reader. My only experience in scanlating has been typesetter and redrawer, and even in those areas I have very low standards anyways.
Pages 13 and 14 make no sense. I'm just gonna write the lines here, and ask if someone can make heads or tails of it:
"A beautiful girl by the sea. A White one-piece swimsuit would suit you well. I wanna buy you one."
"It was just like that when you sent clothes to your little sister and refused them, saying they weren't her thing. It's in this way that being charmed is somewhat obnoxious. Though I don't particularly think that you're at any risk of doting on me like your little sister. And there's no sexual charm there."
"So does that mean... does that mean you'd be happy to let me pet you...?"
"I did not say a work to that effect."
The joke is supposed to be that Jinguuji is fine with being seen as a little sister, so long as there is no sexual tension between them. That's why Tachibana interprets this as a free pass to give her headpats. That's it. But what the translation actually wrote in the page is almost the opposite.
For starters, Tachibana is talking about a one piece dress, not a swimsuit. It's just a fictional dress that manga uses to depict cute girls in the summer, it comes up again in later chapters. It seems like a small detail but it turns the next sentence into nonsense.
Tachibana says he wants to see a beautiful girl in a swimsuit, and somehow Jinguuji interprets this as completely chaste sibling behaviour. But then she inexplicably changes her mind and says Tachibana -doesn't- see her as a sibling. That he's "in no danger of doting on her as a little sister". Then she changes her mind again, and says he DOES see her as a little sister, since there's no "sexual charm".
Am I crazy? I mean, I think there's enough context in the story that I sort of understood the joke but holy shit, a proofreader would've been so useful! Whatever comedy the author intended was buried in the awkward structure of that exchange.
Mind you, this is the only time I'll ever complain, because I love this manga to pieces. I'm incredibly grateful for new chapters, so I'm glad there'll be more releases, even if a couple lines make me sractch my head.