I was really stupid today, and even though I told myself I wouldn't do it after I purchased my tickets, I checked the prices for flights home again today.
The exact flight dates I wanted Aug 1-Aug 18 were available, direct both ways, for $200 less than I paid!!! For the flight I booked, I have to change at Vancouver, and I'm leaving Canada on the 19th (meaning I have to use one day of nenkyu more than I had originally planned)!! ;_;
Oh well. On the bright side, this means I have one more day to be at home and to hang out with people.