Ah, one of those total non-endings. At least it didn't end on a cliff-hanger, but it still feels annoying to not even have the ending acknowledged at all.
Hell, it'd be pretty easy to make an ending for this; set it in the future on the date when everyone reveals they were a girl except MC, or show it even further in the future and show MC's relationship with everyone now (maybe it's a school reunion?), and who he shacked up with.
Anyway, cute idea that didn't get to live up to it's potential out of ten.
Quick extra note: The extra chapter seems to imply, maybe, that there will be more?