Kiki can be found ingame in HKO in Paris in the Pantheon, together with Lala, his twin-sister. The Pantheon does not need a key to be opened. He will give you a bit different quests than his sister.
At the Dream Carnival, Kiki is not with Lala but a little further away. You may want to seek him out to help Lala, who will give you quests at the Carnival - try to find Kiki afterwards! Kiki likes spring and summer, he loves to look down on fields of flowers like dandelions from high above riding a cloud.
Kiki is very curious and a little cheeky sometimes. He likes fishing for stars and exploring planetes - like the earth. He came to earth with permission from Mother-Star and Father Star with the help of Lala's wand. Both twins like to spread happiness to everyone.
The twin stars were devised by Sanrio in 1975.