While the four Kais (King Kai, West Kai, South Kai and East Kai) are ruling in the four segments of the galaxy, Grand Kai oversees them all. Grand Kai is portrayed as an aged hipster, usually wearing jeans and a denim jacket and constantly list
Goku is brought to Grand Kai in the beginning of the Great Saiyaman Saga by King Kai. His home is the Grand Kai's Planet. He is considerably stronger than the other Kais and is known to be the greatest fighter in the Galaxy. Even though he is the teacher of the greatest warriors in the multiverse, Grand Kai (much like King Kai and Master Roshi) is more of a sweet and a kind grandfatherly figure than a traditional disciplinarian. Paying no heed to respectful-but-cold formality, he lovingly treats his social-inferiors as equals and dotes on them as if they were his own grandchildren. In the Japanese version, he affectionately addresses younger warriors with suffix of "-chan" (e.g., Goku-chan, Paikuhan-chan), a term of endearment usually reserved for young children.
Although Grand Kai does not appear in the manga, a Dai Kaio is mentioned there. In fact, his characterization in the anime was suggested to the production staff by Akira Toriyama himself.