
i think he’s just very protective of sachi. raimu is a very troubled character, and the future chapters will be quite telling of that.. i won’t get into spoilers for obv reasons :’)
sachi is letting raimu know the resources available to her, and she is not taking advantage of that. there’s some people that even when the help is in front of them, they won’t take it because of their pride, they simply don’t want to, or they think they don’t need it. it can get a little frustrating to try to help someone when they ask for it but they don’t take any of ur advice. i don’t think it’s fair to sachi to have to share this burden with her even more that she has when she has already offered the help she can give her. sachi is 17 and raimu is 19, this kind of stress should not be put on a high schooler, especially not one that is so close to giving birth. sachi has already extended her help to her, saying she will be there for her and shared what raimu can do.
i think her brother, while we know is a bit close minded, is also just trying to look out for her and caught a bad vibe from the whole situation (i mean she blocks sachi just for not coming to the restaurant without even trying to hear back from sachi). domestic violence is 100% very concerning and someone in that situation is not inherently “bad news”, but i think his perspective is that he just didn’t want sachi to come close to such a dangerous situation (shes still so young and im sure he feels a bit of an obligation as an older sibling to protect her).

i just want to clarify, i do sympathize with raimu. she is in an abusive relationship, and none of the things happening to her are justified, even if her personality is questionable. no matter what, no one should go through that, but it is important as a third party to maintain your distance to protect yourself when you are going through your own stressful times. there needs to be a balance for these things.
from the get go, raimu has a bad mindset about her pregnancy and was under a very common impression that this pregnancy saved her relationship with her boyfriend. they were supposed to break up until she got pregnant. besides the help related to raimu’s pregnancy that she needs, she also demonstrates a need for therapy just in general for her life, mental health, and the way she processes things. raimu needs substantial help, but sachi did what she could as a young girl who is also dealing with the stresses of pregnancy, acceptance, and her future life. sachi’s own family just started becoming accepting of her own pregnancy, so it is a bit of a stretch to expect them to all of a sudden want to help every pregnant teen they meet.
honestly, I'm hating the brother more and more. a pregnant woman getting beaten is "bad news"? no regardless of her messy situation, she's someone who needs help. that's bc of mindset like this that the number 1 cause of death for pregnant women is homocide