Haibane Renmei, Houseki no Kuni Recommendations
both focus on the youngest/ newest person of a special type of people (winged people or gems) developing their identify in a world different from our own. both develop abilities throughout the show from understanding the world around them
Both have a similar calm air to them, as well as moving through the plot in a mellow way, and leave the viewer at a point where the end goal of the series is not predictable or clearly present.
Very similar in premise and progression. Both are supernatural slice-of-life series that focus heavily on character and world-building. Both feature a cast of characters who cannot fully explain their origin or purpose, who are subject to a mysterious and occasionally suspicious power structure. I reckon Haibane Renmei does it better - it's very nearly a masterpiece, even if it starts slow.
If nothing else, these two shows are conceptually similar with a strong story focus.
BTW: The english dub of Haibane Renmei is great if you care
A crucial part of Houseki no Kuni core identity could be summarised as a a buddhist parallel to Haibane Renmei.