Ken Midori, known in Japan as Kensuke Midorikawa, is a central character in the Beyblade Burst series. He is a young blader who initially presents an eccentric and somewhat intimidating front, but this is eventually revealed to be a mask for his true, deeply shy and soft-spoken nature. A significant reason for his shyness is his family life; his parents travel frequently for work, causing him to change schools often and making it difficult for him to form lasting friendships. To cope with his social anxiety and communicate his feelings, Ken has developed an extraordinary talent as a ventriloquist.

Ken is rarely seen without his two hand puppets, a blue, sharp-toothed dog named Keru and a brown, floppy-eared dog named Besu. These puppets act as extensions of his personality. Keru is used to voice Ken's more aggressive, rude, or passionate thoughts, while Besu expresses his kinder, gentler, and more humorous side. This unique method of communication makes him difficult for others to read, but underneath it all, he is a friendly, supportive, and sensitive individual. Over the course of the series, Ken gains confidence, becoming more assertive and eventually learning to speak in his real voice without the aid of his puppets.

Ken's primary motivation is the desire for true friendship and connection, a need that is initially fulfilled when he meets the protagonist, Valt Aoi. Valt persistently reaches out to Ken, recognizing his loneliness, and becomes what Ken considers his first real friend. This friendship is a cornerstone of Ken's development. He holds a high level of respect for another blader, Shu Kurenai, to the point where he agreed to join the Beyblade Club only for a chance to battle him. Shu is also the first person Ken spoke to without using his puppets, highlighting their bond, which makes a later incident where Shu, while transformed into his alter ego Red Eye, rips the Besu puppet all the more devastating. Ken also moves to a new school and is invited to join Team Beasts by its captain, Ben Azuki, whose encouraging and wild spirit helps Ken become more self-assured.

In the story, Ken first appears as a mysterious and powerful rival before becoming a key member of the Beigoma Academy BeyClub and later a member of Team Beasts. His role often centers on his personal growth as he learns to overcome his shyness and become a more confident blader and reliable friend. Ken wields the Beyblade Kerbeus, known as the Guard Dog of the Underworld, which is designed for defense and stamina. His signature special move is the Chain Launch, where Kerbeus uses its chain-shaped layer to chip away at an opponent's stamina, a technique that can be used both defensively and offensively. His Beyblade evolves over time, with later iterations including Chain Kerbeus. As a blader, Ken is shown to be highly skilled but can become nervous under pressure, a flaw he works to overcome with the support of his friends.