<font face="Verdana, Arial, Helvetica, sans-serif" size="2">The NRT-ITM flight is a 747-400. From seatmap.com, it looks like rows 16-25 are configured as if it were business class but sold as Y.</font>
This would be the
Super Seat section, accessible for a moderate premium over regular fares. No idea why your domestic leg got booked in Y; ANA seems to market this more as a comfortable seat than as a bona-fide business class, though.