Passenger routes do not interfere with each other.
But...
Tokyo Haneda is a 99% domestic/regional airport in AWS, while Tokyo Narita is mostly international. From what I remember when I played in Japan not too long ago, the demand between Narita and other Japanese airports is very small (except maybe a few major airports), or even none for the smaller airports. But Haneda has an enormous domestic demand to other Japanese airports. (as you have probably noticed while looking at their demand)
Same thing for Itami and Kansai that serve the city of Osaka, but I remember Kansai has a decent amount of domestic demand too.
You are better off flying from Kansai to Haneda, but if there's unserved demand between Kansai and Narita, feel free to fly there too.