Karen's cloned sisters appear in Trial 3: Deep Blue Girl and speak in musical tones. They live deep in an abandoned undersea lab. Because Karen and her clones never age past a certain point, none of them are likely to be the age they appear to be.
Nine girls with different clothes and hairstyles. Almost all of them wore skimpy outfits, mostly nothing but their underwear and lingerie with black socks. Some of them also wore pink panties like Karen. They first appeared when Eri and Aika were investigating a computer terminal in the cloning room. They attacked with screwdrivers and pocket knifes, trying to force the intruding pair to leave.
The clones had superhuman athletic ability, able to leap clear across large rooms in single bounds or skip in long floating arcs in defiance of gravity.None of the clones seemed to be able to make normal speech, instead making strange musical noises when talking to one-another. Despite this, they were still able to make gasps, moans, choking sounds, and yelps like normal girls.
The smallest clone, though not the weakest, she vaguely appears to be a preteen girl. She wears a hip-length, dark blue blue chemise with a white bow on her chest, white bobby socks and white midleg panties with a blue bow on the front. Because of her small size and cute appearance, she wasn't very threatening and was easily underestimated.
It is unknown if Little Karen's small body is an accidental defect, her creators designed her to look like a child, or she actually is one. The few official words on the question seem intentionally vague.
She first appeared while Aika was distracted fighting the other clones. Eri didn't take her seriously and told her to get out of her way, but Little Karen waited until Eri walked past to jump in the air and knock her out with a kick to the back of her neck.
Aika noticed, but was too busy being attacked by the other clones to help. Little Karen then entertained herself for a while by pulling and poking Eri's cheeks. Eventually Eri began to wake up and Little Karen pulled out a knife to stab her. By this time Aika had finished defeating the others and threw a screwdriver at the small clone's wrist to distract her, then demanded she leave Eri alone. After staring at Aika for a moment, Little Karen leapt across the room to attack her.
Aika easily counterattacked with a leaping kick to her gut that sent her flying backwards. While she soared through the air her dress lifted up and billowed open, exposing her panties and right breast. She landed on her back next to Eri with her skirt hiked up and the camera level with the floor aimed roughly between her raised legs. Stunned and dazed, she lifted her head and stared ahead unfocused in a seeming attempt to get up, but Eri swung her arm down on her and struck either her stomach or her neck. Little Karen choked and pushed down with her legs, thrusting her lower body into the air and making her dress slide even farther. Then she sighed and passed out, falling back down in a starfish position, chemise up past her stomach.
The final time Little Karen is ever seen is a distant low-detail shot from outside the cloning lab as Aika was trying to pull Karen out of the scanning table and escape Giant Karen. Little Karen is alone on the far right side of the room opposite all the other clones.She is the last enemy girl defeated in R-16, the only girl ever knocked out by Eri, and possibly the youngest character to appear in the Agent Aika.
The largest and strongest, she is the only enemy in the series never KO'd and likely the only character aside from Shivie Nina that could fight Shivie Aika and beat her. Due to her towering height, she is completely naked. When Eri was still distracted with her surprise KO of Little Karen, the large clone came from out of nowhere and grabbed her. She then began to squeeze the life out of Eri, only to throw her unconscious body at Aika and walk towards them.
Aika grabbed Eri and tried to get out. She removed Karen from the scanning table, causing the doors she kept open with her body to start closing. However, Giant Karen's immense strength let her grab the doors and pry them open. Seeing no other option, Aika dared to try and fight the giant, kicking her fingers and frightening the huge clone for a moment. Aika then used the distraction to kick Giant Karen's toe, but this painful attack only enraged her. Too fast for Aika to react, the clone kicked her into a wall and knocked her out, causing her to fall to the floor face-down with her skirt flipped up. This is the first time Aika ever passed out in a manner like the many women and girls she has and will knock out in her life.
Before the giant could reach out and grab Aika, Karen herself woke up and stopped her by revealing that she knew how to use the musical clone language. Karen managed to convince Giant Karen not to kill her friends, and the large clone agreed to tell her about her origins. She then allowed all three of them to leave unharmed. She was also nice enough to pose for a photo with Eri, but she's so huge that only her leg was visible in the shot.
Giant Karen presumably cared for her unconscious smaller sisters after Aika's group left. All the clones then went back into hibernation as the facility shut down, seemingly for good. Why none of them chose to leave with Karen is unknown, but it's possible that Giant Karen was incapable of leaving by normal means due to her enormous size and her sisters didn't want to leave her behind.