The Pixellation on the object in Hatsuo's hand in the OAV is a wonderful use for misdirection purposes. It helps steer the viewer's perception in the wrong direction by concealing that it was most likely just the device she used to tie him down.
Based on what Maho and Mizuho remember about their father, Maho may actually have been born first, although Mizuho is clearly older physically and emotionally. (How space travel affects the rate at which the various travelers age is never really much explained or discussed, but it's hinted that there is some time dilation.)
Possibly bolstering this theory, Ichigo tells Kei her little sister passed her by while she was comatose, growing up and getting married while Ichigo remained stuck in adolescence.
