Kaiba is a science-fiction story about a universe where all living beings physical bodies are nothing more than a surrogate to their mind, which can be extracted and put into a new body.
The series begins as the main character, Kaiba, wakes up and finds out that he has suffered from traumatic amnesia. Knowing absolutely nothing of himself, he is giving a single clue of a photo of a woman inside of a pendant. He is thereon ventures around the universe trying to find out who this unknown woman is and who he is.
From the get-go, Kaiba confronts you with its simplistic cartoon characters, these at first come off as something childish and innocent on the surface, and may convince some that its childish in character and storyline, but instead becomes more darker after watching the first episode.
Kaiba doesn't treats its story or characters as other science-fiction anime do. Instead throughout the entire anime wants to shock its audience with the harsh and brutal world in which people live in, juxtaposing its simplistic visuals.
Each episode is filled with new characters and new worlds in which Kaiba experiences first hand. Sometimes showing the world and its people on how exploitive and sinister they are toward minor characters and the main characters. Some themes that are tackles like surrogate stealing, prostitution, harsh violence and human suffering are executed perfectly with nothing holding it back.
Every episode focuses many on some of these topics and it into the very details of the character who suffer gravely from it. Characters express themselves with personality and expression, even if the character is only featured in one episode the writers have carefully crafted it to help flesh out such characters.
It only goes to show that anime can convey such a masterpiece with conventional methods and express something far more visceral, frightening and amazing enduring. Without having to resort to old cliché and exhaustive methods of expression.