This was a decent one. The ending didn't land, but I'll definitely take that over an evenly-paced story that doesn't set things up the way this one did. This one actually feels like it could be expanded into a decent story. Like maybe a whole plotline where the supportive fanclub discuss expelling him just so he can romance her.
Their early dynamic made me laugh quite a lot, but it sounds like a lot of folks don't like it mainly for the weird idol-mentality that's mainly in Japanese culture. It's also a bit iffy for me, but knowing the context makes their interactions funny because it's a non-toxic idol fan being an extremely diligent otaku while she naturally has no fucking idea what any of that means.
Though I think the way to make it a peak story is to cut out the romance aspect. Fully make her aroace and lean heavily on it for her delight in living in a monastery. Then, rather than making her marry him, have her either get taken in as a maid in his house or become a nun specifically in his territory.