Yuuichi Jin is an A-Class (formerly S-Class) member and also a member of Tamakoma Branch. Yuuichi has brown hair and blue eyes. He wears a sunglasses on top of his head. He is always wearing his Border uniform, a blue jacket with a long black stripe going down the middle of each sleeve. He seems to enjoy Bonchiage, and is frequently seen eating them.

Yuuichi has a laid back demeanor, even in situations when he is called out for being an antagonist, such as hiding and protecting a humanoid Neighbor. His favorite food being rice crackers, he always has a bag in his hand wherever he goes, offering some to everyone, even people he once fought with. Despite losing his mother to a Neighbor, he thinks that not all Neighbors are bad guys. In fact, he thinks humans and Neighbors should become friends, showing that both races could co-exist. Yuuichi always acts like a carefree person, but in order to protect his friends being threatened, he shows a much more serious side. Even then, he holds back when he has no desire of harming his foes, unless they force him to.