Keebo is voiced by Lucien Dodge

K1-B0 is a robot, having a fully mechanical body. Most of his body is made up of black metal resembling armored plating, and he does not wear clothes. He has two glowing spots on his chest, another two on his stomach, and two on his both wrists. He has platinum blonde hair. His waist, which resembles a belt, has a glowing red spot on the each side of his front. He also has quite a short stature.

K1-B0 is a polite and serious teenage robot, who has some trouble with human social interaction, and often comes across as unintentionally comical as a result. According to Kazutaka Kodaka, K1-B0 has both cute and cool characteristics, with him being socially awkward but serious. Nevertheless, K1-B0 takes pride in his form and often boasts about his wonderfulness and efficient functions, though the other students never seem to find them impressive much to his disappointment. His aim is to overcome being an ordinary robot and because of this, he may get offended if he is compared to much more simple machines. While generally well-mannered, he is quickly angered by any prejudice against robots and sometimes threatens to sue people who make "discriminatory remarks". He considers robots a minority group among humans and can get slightly paranoid about "robophobia", supposedly because of past experiences.

Since he is a maturing AI, K1-B0 learns and develops similarly to a human, making him an unique existence. While he has no heart nor brain, he uses his calculations to speak "as if he had a heart". Even still, he often can't read the mood around him and is oblivious to things, sometimes taking things very literally and occasionally acting insensitive. Due to being overly serious about certain topics and unable to understand sarcasm, he is an easy target for bullying and it's easy to make him heated up, and he is rather easy to read. According to Izuru Kamukura in the bonus mode Ultimate Talent Development Plan, K1-B0 has a tendency to rely on others in difficult situations, and he overall gets very nervous in bad situations. Furthermore, he feels a bit self-conscious about the fact that he cannot strengthen his body on his own like humans, and he needs help for maintenance and upgrades. Overall, he is a bit conscious about being unable to do some things humans can, causing him to act condescending towards humans at times and proclaim that he can do lots of things humans cannot. In Chapter 4, when the students enter the program world, K1-B0 appears disappointed and secretly wished he would have a human body. In Chapter 5, he is seen wondering his existence and being very interested in whether or not he is considered a person by the hydraulic press' safety function and Miu's Electrohammers, and even wants to test them despite the risk. In one scene, he is scared of the idea of a huge mecha suddenly appearing, not realizing the irony of it. He himself has also pointed out that he doesn't really like "sci-fi" things, even though his existence alone is quite sci-fi, and he would rather be more like other people instead of possessing things like rocket jets. He greatly loves Japanese culture, including Japanese food (though he can only look at it), kimonos and wind chimes. However, he also feels insecure about being too ordinary and not deserving his title as the Ultimate Robot, which is why he has a dream of becoming a pop star or doing some other type of work. For a short time, he even considers becoming a "tragic hero" figure in order to become more interesting, with a new tragic backstory and weapons, even though it's not something he would like. In general, he has a strong desire to be accepted and be like everyone else.

K1-B0 seems to understand most human emotions and many of their habits, though some of them only in theory, and he prefers to make decisions and actions based on logic. He claims that he works very hard every day to understand human emotions, and he's often quite hurt and saddened whenever the other students tell him that he wouldn't understand something because he is a robot. He tends to find abstract ideas frustrating and difficult, and sometimes has a hard time understanding why someone would do something that is very illogical. In general, he can get confused and a bit uncomfortable by his strange classmates, and sometimes reminds them to speak in a way he can understand. He can also get some habits a little wrong, like confusing the action of handholding and handshaking. Like a human, he blushes when he is feeling shy and feels awkward when talking about something inappropriate, though occasionally he may say inappropriate things without realizing it due to his naivety. For example, he considers nudity very shameful and embarrassing, but doesn't seem to see anything inappropriate in going to the bathroom, as he sometimes casually tells his classmates they're free to do that if they are close to a bathroom or even telling them they can do it right there even if they're in public surrounded by people, seemingly trying to be polite with this gesture. He can be very expressive with his body language since as a robot he can move his ahoge and some other parts according to his emotions. Being a robot, he is also very innocent when compared to most teenagers, and some situations make him very nervous and shy. In Chapter 3, he claims he is ticklish and it's implied that he might be able to feel pleasure similar to sexual pleasure when sensitive spots underneath his armor get touched. In general, he doesn't seem to have very much interest in sexual matters, considering it quite scandalous and claiming at one point that he would never expose professor Idabashi's strong AI to pornography. He has also bashfully pointed out that there isn't much he can do about it anyway, since he lacks any reproductive functions. However, he secretly seems to have some interest in such subjects, as he once accidentally admitted this without thinking. When he is asked about his ability to fall in love, he says he doesn't know because he hasn't had any romantic feelings yet. In the bonus mode Love Across the Universe, it's eventually confirmed that he can fall in love and dreams of romance and intimacy. In the topic of romance, K1-B0 is shown to find the idea that robots should only date their own kind very offensive. When he does develop romantic feelings, he is shown to be very serious and surprisingly bold about the matter, assuming that you constantly have to do typical things couples do and be very dedicated in order to truly understand love. However, he is simultaneously very shy about the subject, as he gets very embarrassed, blushes a lot and stutters when he just asks to hold hands. He also seems to consider the maintenance Miu performs on his body very intimate and he is very embarrassed about it at first, especially if it's mentioned in front of others, as if it is a sexual relationship (though, it does resemble a one). While he doesn't speak to Miu in explicitly romantic manner, he does care about her a lot and even gets jealous of a computer.