The majority of the story is about healing from brutal trauma and thinking affectionately about found family (who are mostly not human). Interspersed with Sonia dishing out brutal violence back. The LN chapters were short, and the manga chapters are fairly simple. Enjoy the scenery and angst but don't expect many events. There's lots and lots of familial love, and no romance.
The romance tag is probably a holdover from an early version of the WN where the main characters were both about 20, with a 4 year age gap at most, while in the LN and manga they are 15 (mentally under 10) and 25 or older. The only characters who ever interpret the found family parent-child or sibling-like relationship as romantic aren't good people.
I'm not sure about that tag for the second arc when the saint Sonia is more or less rehabilitated and even more overpowered, but I put off reading for now. The time skip felt like a disconnected wish-fulfillment story, though I trust the NU tags that it's still not romance.