Haikyuu is a volleyball anime and manga series following Karasuno High, where Tadashi Yamaguchi is a first year pinch server and Kei Tsukishima, nicknamed Tsukki, is his close friend and teammate. Gomen is Japanese for sorry, so the clip became a compact fandom shorthand for their friendship. Shared on anime soundboards alongside other short character catchphrases like nico nico nii, it survives because fans recognise both voices and relationship from one word, making it useful far beyond the original scene for edits, streams and chats.