ココロ

Shiranui talks with his inner-self, Kokoro when he’s unconscious. His heart, which is this mysterious girl, is the driving force for his unwavering will. 

She is actually the used-to-be terminally ill little sister of Hoan Wenje/Phantom Killer; a Chinese girl by the name of 皇千慧 (Hoan Chenfui) who always wanted to travel to Mars, and -after proper legal procedures- whose heart was transplanted into Shiranui following her death. The real reason Shiranui always looked for a way of getting to Mars is her.
Meanwhile her older brother, Koe also decided to pursue her dreams, thus ended up in the Mars project himself too, and he's unaware for a good while that his good friend and colleague, Shiranui was the recipient of Chenfui's heart. Upon finding out the truth and after Tempest's persuasion he swore revenge against Shiranui as he blames him partially for her death./

Unfortunately there's no route for her even though she's a crucial key character with a lot of screentime.

Edited from url=http://whatistomato.wordpress.com/2010/07/09/a-tribute-to-evolution/Warum's review.