Even if North Korea doesn't enter Ukraine itself, them being in Russia frees up Russian soldiers to attack inside of Ukraine either way, meanwhile Ukraine has to keep soldiers along the Belarusian border in fear of Belarus invading and along the Transnistria border in fear of a Russian attack from there too, we can't even do the bare minimum in response which is to protect our own airspace. And if North Korea helps Russia push Ukraine out of Kursk there goes Ukraine's only win in the past year and once again puts Ukraine at a disadvantaged negotiating position.