Officials at Tobu zoo in Saitama, north of Tokyo, said Grape passed away after a brief illness with the object of his desire right by his side. He would have been around 80 in human years.
Earlier this year, the Humboldt penguin became smitten with a cut-out of Hululu -- a character from the Japanese anime "Kemono Friends" -- after being dumped by his former mate, a female called Midori.
The plight of the romantic penguin went viral, earning Grape millions of fans worldwide.
A steady stream of mourners has visited Tobu zoo's penguin enclosure, many with flowers, since the tragic news broke yesterday, while officials erected a makeshift shrine to their fallen celebrity today.
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"Little Grape had a wife called Midori but she left him and found herself a new husband," Tobu zoo's penguin caretaker Eri Nemoto told local media.
"We put the cardboard panel next to him to comfort him to the very end."
"Goodnight sweet prince," wrote one Twitter user, while another posted: "You charmed the world and made it a little brighter. See you, Space Cowboy.
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