@pikaryn I think from the first few chapters, it's said that it's because he thinks he is ugly inside and out, that he believes he's a monster, so she deserves better. But she thinks otherwise thankfully!
...somehow this is the first time that I think that the polite way Erden speaks to her sounds kind of beautiful... Usually I think that it sounds kind of cold or like putting a barrier in between and it unreasonably irks me (🤣🤣🤣 yeah, I know it's silly)... Maybe seeing him fangirling (?) over his wife helps to mitigate things? 😅