Youko is Shinji's girlfriend, but is also stated to be free to do whatever she likes as we see her with Haru. Her true feelings, however, reside with Shinji as is shown when Shinji brings Hirota back to the headquarters on a date. She really cares about Shinji, but he sees her as nothing more than a 'thing', really, especially with her lack of commitment to one man. She eventually causes a rift between Haru and Shinji that partially causes Haru to leave, only to come back and be killed.