Yeah, there's a specific fare that requires leaving on that special AC13 flight.

The cool thing about that fare that you can come back any time on an TYO routes woth P space.

Can't remember the fare rules.

Also, always always always check all the rules to the max. It is absolutely not rare that the booking flow will say $X for changes and cancellations, but the fare rules show $Y. One or the other may be more in your favour do keep an eye out.