Kim Jaehyung is a junior at Hope's Peak High and one of Kay's companions. He is known to be vulgar, cocky, childish, energetic, boastful, idiotic, hot-headed, rash, and comical. Kim was known for his abusive and brash behavior and his rude and disrespectful attitude towards adults, kids, and even those with special needs. This was due to his emotions constantly spiraling out of control and feeling anger due to jealousy and rage whenever someone is more loved than him, which he never feels like he's always unloved by others. However, Kim never bullies Kay, but does sometimes intimidate her, which she's simply unphased. There was one time where, before all paras were removed from their position as the school's special needs carer, Kim pushed off Guppy Vokita, a kid with special needs and diagnosed with Baby Toddler Syndrome, and causing him to tumble down painfully from the tall, wide open stairs of the school connecting to the 1st and 2nd floor while still on his wheelchair and hitting the ground hard. By the end of it, Guppy was seen bleeding from his head as he screams painfully as Kim manages to slip by without anyone noticing. Thus, Guppy's push was ruled out as an accident. Kim's reason for this? Guppy's constant singing and the fact that Guppy laughed while looking at him due to showing expressions of happiness, while Kim took it as mockery being thrown at him from Guppy for being a bad seed to society. Years later, after the paras were removed and replaced by the Neko-Kittens, the 3 students who witnessed Kim pushing Guppy off decides to get revenge on Kim by doing the same thing he did with Guppy and humiliating him in front of all the students. However, Kay saw the video of Kim's death and rushed in to push Kim away just in time before she herself gets pushed off in his place, much to the three students horror and everyone else in the school building. She survives, but is now fatally wounded and in critical danger. Kim, witnessing this and feeling utter distraught since she's the only one that means something to him, became enraged with the 3 students, causing a rift of the Caligula Effect and spontaneously forges his primal weapon: Dual Fist Mallets. Pummeling the 3 to the ground, he makes his way to Kay's aid. Kay manages to regain consciousness and recovering rather quickly, with Kim on her side constantly and becoming anxious and tense. Kim thanks her and apologizes to her for being pessimistic and arrogant towards her, which she already accepted long ago. Since then, Kim changed to what he is now today, and becoming a companion to Kay and as her best sidekick. While Kim is known to be very hot-headed and easily pissed, his heart is sure made up of pure gold.