Thread:LeXuS008/@comment-211667-20190409145829/@comment-211667-20190409211744

That one is ok, as in the LN raws its like that as well, not sure why though. But, its not a translation error, that's for sure.

Maybe, it got something to do with an event that happen later on, as there is around a timeline gap of 1000+ years between "Zero" and "Main Series". So maybe Miledi either started calling him "O-chan" sometime during "Zero" timeline, or later during her 1000+ years of isolation in the Labyrinth.