It's like when two schizophrenic people validate each other's fears of gang stalking or insisting you don't need a driver's license because of maritime law. This codependency is not healthy. Doubara is essentially hiding where Mio is from her friends and family. He's behaving more like a kidnapper or predator than a friend or ally. That the author is trying to depict this as romantic is even more insane.
... no he isn't. That's what caused this break, him realizing that he was using her because he was desperate to keep her nearby. He's following her wishes at this point, she's afraid of her husband(for, as we've seen, p. good reason) so she wants to keep hidden from him.
He didn't say he believed the same thing. Something I don't know if he ever
really said, just tried really hard to imply. When she told him over the phone that she still thinks her son re-incarnated, all he said is that he knows she does. That her belief doesn't stop him from wanting to help her.
She's reaching out again to him because, well, so far he's the only one who has done something other than blow her off, get mad at her, or ignore her belief. While we can look at it harshly as indulging in delusion, I think that Dobura has always
hoped that by getting Mio to read the things her son loved, she'd find some sort of connection and closure. Or maybe that's just my thoughts about all this, I haven't re-read the manga before I made this post.
There seems to be a real Poster's Disease where manga with pretty clearly good people, who are flawed because they are people, trying to do the right thing get some real contrarian posts.
Cause like fuck man this chapter rules and Dobura instantly setting aside all his previous doubts and guilt when Mio called him and saying he's on his way was a really great character moment. Cause he even realized that what he said didn't make any sense afterwards, but his instinct was to assure Mio that he's there to help, even though he spent the last... 4? 5? Chapters beating himself up for what he did.