Cousin is a dark pink/magenta cousin with an outfit that looks a lot like a school uniform. Their antenna has a pink heart on top instead of a red ball. Cousin also has blue/sea-foam green skin, making them closer to the coloration of Opeo than the other cousins when it comes to their complexion. Cousin's head is not one of the typical shapes as it is sort of bean shaped, or possible supposed to look a bit like a heart.
Cousin is able to switch outfits at the end of certain datelines, but not during the actual gameplay, as they are only shown in the end images of the datelines after the credits roll.
Not much is said about Cousin's background before entering Namco High, but what we do know is that they have a slight jealousy of the Prince (because they wish to be like him). Unlike most of their cousins, they seem to be a bit nervous about using a katamari again. It is revealed in Mr. Driller's route that Cousin actually has a passion for rolling, and became hesitant to roll a katamari again not because they got in trouble, but because (unlike other cousins, especially Prince, who will continue to try even after being scolded by his father, The King of All Cosmos) they worry about the damage they cause and the people they injure in the process of it. Cousin is never shown meeting any of their cousins, but it is assumed that in some way that they know them because of mentioning the Prince.