Yena used to be a blurred girl in LOONA TV prequel. (source: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-C7q4JGZOXyI.html) I don't know much about their tradition, but if consider that she used to be in the same company with Yves, she is sunbaenim.