It is recommended to read up to Droid #9 and Milady #3 first.
Story takes place over at least a few days, with each 'arc' taking place in a day with some undisclosed time between them. Author originally splits the arcs as intermission arcs after Droid #7, Strong yet Beautiful, and Droid #10, making the splitting more apparent when reading the Droid series. Meanwhile for the Milady series all three crossover arcs are fitted between Milady #3 and #4 (but the x-over events occur chronologically after #4). Hard to make it work with Danbooru's pool system though, since splitting a subpool into pieces in one pool but as one contiguous part in the other makes it very easy for readers to accidentally skip ahead while reading the Droid series.
