Grape-kun passed away at the age of 21, just a month before the zoo's Grape Festival, which celebrates the penguin with a series of events.
According to Phys.org, officials at the zoo said Grape passed away after a brief illness and was around 80 years old in human years.
The Humboldt penguin fell in love with the cut-out of Hululu, a character from the Japanese anime Kemono Friends, after he was dumped by his penguin made Midori.
Grape would stare at Hululu for hours on end.
Tobu Zoo's penguin caretaker Eri Nemoto told local media: "Little Grape had a wife called Midori but she left him and found herself a new husband.
"We put the cardboard panel next to him to comfort him to the very end."
HuffPost Japan reports that tributes have been paid online, including a message on the official Twitter of Kemono Friends, saying: "A lovely figure, deeply engraved in the heart."
Pig Beach, or Pig Island, is an uninhabited island in Exuma, the Bahamas, famed for its many swimming pigs. They are said to have been dropped off on the island by sailors who wanted to return to cook and eat them, but never returned. Others say the pigs survived a shipwreck and managed to swim to the island. Today, the pigs are fed by tourists who visit the island to meet its unexpected residents.
Okunoshima Island, in Japan, attracts tourists to witness its huge rabbit population that has taken over the island, with many people visiting to feed the animals. The island, often called Usagi Jima or Rabbit Island, was used as a poison gas facility in World War II. The rabbits were intentionally set loose after the war when the island was developed as a park.
The jungles of Guam have up to 40 times more spiders than the forested areas of the nearby Pacific Islands thanks to the invasive brown snakes that wiped out 10 of the 12 spider-eating bird species. Because the birds ate some of the insects that spiders eat, there is also now more food for the spiders to eat. One of the most common types of spider in the jungle is the yellow and black Banana Spider.
The wild horses on the Assateague Island in Maryland are actually feral but tough enough to survive the scorching heat, stormy weather and poor quality food found on the remote barrier island. Local folklore says they are survivors of a shipwreck off the coast of Virginia. Assateague is one of the few places in America where you can view wild horses and visitors are advised to admire the animals from a distance.
Located just a few kilometres off the northern beaches of False Bay, near Cape Town, Seal Island is home to approximately 65,000 Cape Fur Seals. The island is a popular feeding ground for the great white shark and lucky visitors may see the fish breaching in pursuit of its prey. Seal Island is like a sea of brown bodies stretching and hauling themselves along the rocks. It is too rocky to disembark but well worth observing from a boat.
The rhesus macaques on Cayo Santiago, also known as Monkey Island, off the eastern coast of Puerto Rico, were introduced in 1938 for scientific research. Around 1,200 free-roaming monkeys can be found on the small island and while it is not open to tourists, you can get an up close view of the animals from the water.
The island of Tashirojima, or Cat Island, off the coast of Ishinomaki in Japan has a larger cat population than it has humans. The people who live on the island are those who take care of the cats. To the locals the cats represent luck and fortune, and there is even a cat shrine at the centre of the island, along with cat-shaped cottages. Cat-loving tourists are welcome to visit the island, but dogs are not allowed.
Every year during the wet season (October to December), Christmas Island's adult red crabs begin their migration from the forest to the Indian Ocean where they breed and spawn. With tens of millions of red crabs living on the island it is possible to witness them pour out of the jungle and take over Christmas Island. The phenomenon lasts several weeks, forcing roads to close for the crabs to cross.
Norway's famous bird island, Runde, is teeming with birds - more than 500,000 that visit from February to August during the nesting season. Bird mountain, with its cliff formations towards the ocean, is dominated by Atlantic puffins. Their nesting season is between April and August, when 100,000 pairs of puffins can be found on the western side of Runde. Outside puffin season, they stay at sea along the coast.
The tiny uninhabited island of Ilha da Queimada Grande, off the coast of Brazil, is definitely one to avoid as it is teeming with one of the most venomous snakes on the planet, the Golden Lancehead Viper. Every three feet, one of the snakes is lurking, terrifying generations of fisherman. Currently, the Brazilian Navy has banned people from visiting the island but occasionally scientists are granted access.
There are approximately 3,000 polar bears and just 2,642 people in the Svalbard archipelago. A large number of polar bears are found on the surrounding islands east of Spitsbergen, yet you should be prepared to encounter one anywhere in Svalbard. As the world's largest land carnivores they are beautiful but dangerous and human encounters often have a fatal outcome. There are polar bear watching cruises which allow you to see the animals from a distance.
Hawaiian island Kauai is famed for its lush vegetation, pristine beaches and… chickens. Roosters, hens and little chicks are found roaming the island and are believed to be descendants of former fighting cocks unleashed during a devastating hurricane which hit over a decade ago. The birds are found in outdoor food courts, ruining sugar cane and corn crops, and even waking tourists at the crack of dawn.