Koharu Mishima (三島 コハル, Mishima Koharu) is a character in Talentless Nana. She's the main antagonist during the arc where the students moved from the Island to the Main Land.
Koharu has shoulder-length purple hair and amber eyes.
Koharu is a cunning individual who ultimately falls subject to her own delusions, unable to tell what is real from what is an illusion. Beneath her front of a smart and manipulative person, she is deeply traumatized and frightened of being alone.
Koharu has the ability to share thoughts and information telepathically with her twin sister, Hiyori. Her real talent, however, is that she is able to create illusions, such as making Nana believe that she had been stabbed. This illusion was able to extend to the rest of their classmates, who all "saw" Nana's "wound." Her most prominent illusion is her "twin," Hiyori. Koharu wasn't aware of those illusions herself, as she had deluded herself into believing they were real.
Koharu's parents were killed by the government, though this was covered up. Koharu suspected as such, but no one believed her. She was taken in by her relatives who mistreated her. Due to her loneliness, she created Hiyori. Hiyori was her only friend, and the two were always together. Koharu says that she was able to manage her rough childhood because of Hiyori. It came to the point where Koharu was deluded into thinking that Hiyori was real, and not just an illusion she created.
Koharu collected much evidence on the Island to prove to Nana that she's the culprit. However, she does not use it to prove it to the rest of the class. Contrary to Kyouya, She prefers to make Nana look crazy by utilizing her talent of illusions and talking with the rest of the students about how suspicious Nana is.