Komaki's schoolmate, but 2 years older than her, Rika is the other main female character of the story. She gains the nickname Queen of sex, from Tsurumi, due to her habit to have sex with anyone who asks her. She doesn't seem to care much about anyone but her teacher: Aoki-sensei. Despite this, he will soon make her realizing about how bad she did trusting him. He will trick her, by forcing her to having sex with many guys which he had a debt with, and she suffer a massive rape. Rika's main motivation about liking having sex with her schoolmates is hidden behind the truth that she also has an alien inside her, and her developed ability is a very sensitive touch. If she likes something, she enjoys this a lot more than common people via her touch, but if she dislikes something else her reaction is way much worse, making her going in a very bad status mixed from darkness and disgust, barely to death. Thanks to Tsurumi and Komaki who save her from that bad experience, she becomes friend with them. She soon develops to be in love with Tsurumi, and using the excuse to hold his hand as to be closer to him. Rika is said to be pure evilness and pure innocent at the same time by Numa-sensei, when he discovers that she wanted to do to Komaki the same abuse she passed through since she sees Komaki as her love-rival for Tsurumi's fight. She is also purposed, by Numa-sensei, of being the mother of his child, but she still seems to have a second thought on it. Hana says that she and Shijo do not have a concept of male or female gender in persons as to threating them as the same way. At the start of the story, she also says that purely loves the contact with the air, staying naked on the roof of the school many times.