Koupen-chan is a character conceived by artist Rurutea, that started life on Twitter in 2017, and within 9 months of inception went on to win a LINE Creator's Stamp award. The character has also been associated with musicians like 打首獄門同好会 (Uchikubi Gokumon Doukoukai).
Koupen-chan has a minimal design based on an Emperor Penguin chick, and often showing no facial emotion outside of blinking and blushing. Most notably, is quoted to say "erai!" ("amazing!") as a catchphrase.