Who Is Ran Mouri ?

Shinichi's childhood friend, she's in love with him but never has the nerve to tell him, when she meets Conan she tells Conan about it. Ran is very strong willed and a great karate athelete. She can beat the crap out of her opponents if she isn't scared or semi-unconcious.She seems to be very strong but she's also very tender and she cries a lot after her beloved has left.

She acts as a very good big sister to Conan and always takes care of him, she does all the housework and cookings for Conan and her dad. Her parents are separated and Ran always tries to make them going back to each other.

Who is Professor Hiroshi Agasa

Professor Agasa drives an old Volkswagen Beetle.

Neighbor to Shinichi's family house. He's good friends with Shinichi's parents. He's also a jolly inventor who designs all sorts of gadgets to help Conan with his detective work. Those gadgets include the voice changing bow-tie, the power-kick shoes, the tranquilizer watch, turbo-engine skateboard, just to name a few. 

Basically, Professor Agasa is Conan's go-to guy and always ready to help. 

Who Is Conan ? (by Gosho Aoyama)

Shinichi Kudo is a high school junior, a clever teenaged detective who capably helps the police solve many tough cases. Unfortunately, in a careless minute, he is poisoned by Gin - a member of the Dark Organization - while secretly investigating them. A drug named APTX 4869 shrinks his body, yet luckily, he isn't dead; his body is just withered into the size of an elementary kid.

Shinichi couldn't tell anybody about this because he knows that people's indiscreetion would cause troubles not only to him but also to themselves. From that moment, in order to dissemble his identity from the mafia, Shinichi gives himself a new name: Conan Edogawa. Conan/Shinichi now has to mix himself among the elementary kids to avoid dangers from the Dark syndicate.

With his detective instinct, he gets involved in, and helps the police solve many complex cases behind the shadow of Kogoro Mori - a private detective. However, Mr. Mori wasn't famous in forensic area before, thus his sudden fame and the simultaneously sudden appearance of little Conan in his home have caught the eyes of the Dark Org., and they've secretly begun to send spies to follow Conan, waiting for an opportunity to silence him.