Why it worked
The video likely gained traction due to its connection to the popular anime 'Haikyuu!!' and its use of visually striking, albeit abstract, animations that are common in fan-made content on platforms like TikTok.
Summary
The video features an animated character with the number 4 on their shirt. Various red, glowing outlines appear and disappear on and around the character, including a ribcage, a broken heart, and cat ears. The character maintains a consistent expression throughout.