Many mangaka have assistants who help them with their artwork. The duties of assistants vary widely; some mangaka only sketch out the very basics of their manga, and have their numerous assistants fill in all of the details, while others use assistants only for specific things. Other mangaka have no assistants at all, and prefer to do everything themselves, even though to meet the tight deadlines assistants are usually needed. Most often, assistants are responsible for the backgrounds and screentones in manga, while the mangaka him/herself draws and inks the main characters. While they are often employed to help with art, assistants almost never help the mangaka with the plot of their manga, beyond being a "sounding board" for ideas. Most full-fledged mangaka started out as assistants, such as Miwa Ueda to Naoko Takeuchi, Leiji Matsumoto to Osamu Tezuka, Kaoru Shintani to Leiji Matsumoto and many others. However it is also possible for an assistant to spend their entire career as such without making the jump to being a mangaka in their own right.