Oh yeah, if he's going to tell her, that's how he'll do it. It's just that, when he tries to explain those things to her with "I'm the ghost of your dead husband possessing this guy", she's going to go nuts and withdraw, even if he preceeded the explanation with intimate details of their life together when they were married. The way to get her to want to hear that explanation is for her to experience that Hazuki is behaving a hell of a lot like Shimao, and has been for some time. She's going to want an explanation for *that*, and might actually ask for one. Having been affected by Shimao possessed Hazuki's behavior, her emotions will be where they need to be to hear the explanation and not completely withdraw. If she's being skeptical, that's when he'd start talking about the intimate details.