Dren is a primary antagonist from the anime and manga series. His original name in the Japanese version is Kish, but he is widely known as Dren in the English adaptation. He is a young male alien, approximately fifteen years old, who belongs to a race that originally lived on Earth millions of years ago before being forced to flee due to environmental disasters. His people now reside on a harsh, inhospitable planet where they live underground, suffering from extreme conditions like sandstorms and high temperatures.

Physically, Dren has a slender build typical of a human adolescent. His most distinguishing features are his bright golden eyes with orange hues and narrow, cat-like slits, his rounded yet pointed elf-like ears, and two small fangs. He has very pale skin, a result of spending most of his life underground, and dark green hair styled short in the back with longer sections in the front bound by red bands. He dresses in attire native to his race, including a dark green shirt with a high collar and puffy sleeves worn under a brown sleeveless shirt that exposes his midriff, paired with black baggy pants and dark boots.

Dren's primary motivation is to reclaim Earth for his dying people. He views humans with disgust, believing they are destroying the planet that rightfully belongs to his ancestors. To achieve this goal, he is sent to Earth as one of the first alien operatives alongside his comrades Pie and Tart. His standard method of attack involves creating Chimera Animas, which are parasitic creatures that fuse with animals or humans to turn them into powerful monsters. He is also a skilled fighter who wields a pair of sai swords, which he refers to as dragon swords, and can channel lightning through them to electrocute his opponents. His other abilities include flight, teleportation, energy blasts, and the power to create multiple copies of himself.

In terms of personality, Dren is a complex figure. On the surface, he presents himself as carefree, playful, clever, and optimistic. However, this cheerful demeanor masks a deeply sadistic and cruel nature. He takes great pleasure in tormenting his enemies, particularly the leader of the Mew Mews, Ichigo Momomiya. He enjoys seeing humans suffer both physically and emotionally, often treating his battles with the Mew Mews as a game and referring to his opponents as his toys. He has a cruel sense of humor and gives Ichigo mocking nicknames like kitty-cat or sweetie-pie. While he is generally very possessive and has a quick temper, he will do anything to protect the people he cares about, showing that underneath his cruelty lies a fierce loyalty to his family and his race.

His role in the story is defined by his initial mission to conquer Earth, but this becomes complicated by his growing obsession with Ichigo. He first encounters her by stealing her first kiss, declaring out of curiosity that he was fond of her. What begins as an interest in a toy soon transforms into a genuine, if twisted, romantic obsession. He repeatedly harasses her and even tries to kill her human love interest, Masaya Aoyama, out of jealousy and possessiveness. His feelings for Ichigo are the catalyst for his most significant character development. In the climax of the series, after his master Deep Blue is awakened, Dren chooses to betray his own leader to protect Ichigo. This act of defiance leads to his apparent death, as he is struck down while defending her. Following the final battle and the defeat of Deep Blue, Dren is revived by the power of Mew Aqua. After regaining his life, he returns to his home planet with his comrades, but not before wishing Ichigo happiness and playfully stealing one last kiss from her, confirming that his feelings were authentic and not simply a shallow obsession.