I was worried after the sudden "childhood promise reminder" in ch31 which felt like a preamble for a super rushed "development"/cop out due to the axe, wasting all build-up accumulated from ch01.
Madoka Akbar, I really should have had more trust in the author, he didn't cop out, the childhood promise only serves as a nudge for Tae to force her unsorted accumulated feelings into shape, and the story ending on a promise to wait until Mai is old enough (with Mai's volition) is okay enough. That is the only proper ending for this series, considering all the things that had happened so far.
(In hindsight, I might have worried too much, not even such brutal axe as the one Tatoe Todokanu received could make tMnR throw away such build-up out the window.)