Did Kim Jong Un say that North Korea is joining Russia and entering the war against Ukraine? No, that's not true: The North Korean dictator didn't make such statement. North Korea indeed condemns America for providing military assistance to Ukraine. However, the war didn't affect relations between Russia and North Korea. There is no official or unofficial information that these two countries are united.
The claim appeared in a video (archived here) was published by TikTok user called @Vklnow on Apr.3 under the title "Kim Jong Un made a shocking statement".
I am now tired of the western world, which is trying to impose its poinf of view to everyone. I fully support what Russia has done and join it. I order to send military assistace to Russia and as many soldiers as they need.
This is what the post looked like on TikTok at the time of writing:
(Source: TikTok screenshot taken on Mon Apr 17 16:43:03 2023 UTC)
On the official Ukrainian website, President of Ukraine Volodymyr Zelensky has repeatedly stated that Russian soldiers have come to Ukrainian land. Throughout the war in Ukraine, Zelensky never mentioned the North Koreans.
The North Korean official websites also do not mention that North Korea is sending people to fight in Ukraine. North Korean leader did not make such a statement publically.
Google search also does not return any results on this topic. Neither official nor unofficial sites confirmed the information.