Helsinki would be a much better connection (sometimes even adjacent gates, although that’s not guaranteed).

If you aren’t getting HEL to come up on booking engines, check that you haven’t accidentally defaulted to Haneda as the destination - I think the HEL flights only go to Narita. (Apologies if that is stating the obvious, but I’ve fallen for it before).

Also for plane spotting, on the way back there is an outdoor viewing platform at both Haneda and Narita.