The clip comes from Majikoi S, the sequel to the visual novel Maji de Watashi ni Koi Shinasai, where Yukie Mayuzumi is a shy swordswoman known for ending sentences with desu and speaking through her strap Mataro. Her birthday line was lifted as a standalone greeting and shared on anime soundboards, especially around character birthdays and fan celebrations. Because the phrase itself is a standard polite Japanese birthday wish, it travelled beyond Majikoi fans and became a reusable cute greeting for anime communities.