Kafka is a quiet, smart and easy-going man in his early thirties. He is the Umagon's book keeper. Unlike Gash's other friends, Tio and Kanchome, whose bookkeepers are celebrities, he is an automobile engineer who has come to work from Germany to Japan, similar to Umagon's roaming from England to Japan.

Kafka first meets Umagon when a dog runs off with his book. He calms the dog and takes the book and holds on to it until they meet again at the Devolo Ruins and battle Dalmos. It is later revealed that he came to meet Umagon at the request of Dr. Riddles which explains the note left by him telling Kiyomaro the location of Zofis' ruin-base.

During the Faudo arc, he gains a crush on Elle Chivas.

Sunbeam has a philosophy to be a "cool adult," and doing things like abandoning Umagon or his friends tend to go against his principles, quickly earning him the trust and friendship of the others. He likes to use the word "groovy" and uses lingo frequently.