Jlienderulo

done

same search: https://www.watzatsong.com/en/name-that-tune/803693.html

i got some more info that may help. The animation is titled "リンセインファック.swf" (i moved it to my main pc). Translates to "Linsane F*ck" (i used deepl). after some more looking online I am very sure the characters are Lyn and Sain from a video game fire emblem (made 2003) looks exactly like them. Can't find any other information online about the this animation. I am not sure how it got on my pc back then, probably downloaded it mistakenly from a program like kazaa. I think it might have came from a website like soundclick, i feel it just aligns with the fact is was used in an old flash animation.