Hello! This game is still in development, and several mechanics and story threads are currently not available. You can find Julian through an event in the Work area, which would eventually unlock the circus! Hope this helps.
pardon me for being dumb, but there's only a put your pets to work and explore option when you visit the town
he will eventually appear if you chose the option “put your pets to work”
Do it twice and he will send you an invitation to visit the circus