The star penguin named Grape-kun broke several hearts as he passed away on Friday in Tobu Zoo in Saitama, Japan, at the age of 21. The penguin was known for his attachment to a cardboard cut-out version of Hululu, an anime character from the series Kemono Friends, who is an anthropomorphic female penguin.

Grape-kun fell head over heels for the cut-out, after being rejected by Midori, another penguin who had been his original partner of 10 years. It was said that Midori was stuck in a penguin love triangle and dumped Grape for a younger male penguin.

Grape-kun’s infatuation with Hululu grew when zoo staff left the cardboard piece near his enclosure and noticed that he refused to leave its side. The poster was originally placed there to promote the anime show, however, over time, Grape-kun spent “long hours staring at Hululu”, displaying how much he liked the fictional character, the BBC reported. 

Just before Grape passed away, he became ill, but due to the visible love the penguin had for Hululu, workers from the zoo decided to let him stay beside his new mate. In human years, Grape would have been 80 years old, 

Unfortunately, the penguin's death happened before the zoo's Grape Festival, an event created for the celebrity penguin, that runs for two weeks.

Fans of the penguin have taken to Twitter to share how they felt about the sad news. One tweeted, "Next time I’m at Tobu Zoo, it won’t be the same without you, Grape-kun. You were so [great] and [fun]. Many will miss you. I do"

There have also been several tribute YouTube videos, like the one below, created for Grape-kun, showing just how much the Humboldt penguin was loved by the masses.