Runa Natsui (夏居瑠奈; born November 7, 1995) is a former Japanese actress and fashion model from Tokyo, Japan. She began her entertainment career as a child model and later gained recognition for portraying Kaoru Shiba, also known as Princess ShinkenRed, in the television series Samurai Sentai Shinkenger (2009–2010). She reprised the role in Kaizoku Sentai Gokaiger (2011) and several films in the Super Sentai franchise. Her other film credits include School Days with a Pig (2008), Lesson of the Evil (2012), Kotodama: Spiritual Curse (2014), and Death Forest 3 (2015). She also appeared in television dramas such as Kamen Rider Fourze (2012) and Angel’s Knife (2015). In November 2017, Natsui announced her retirement from the entertainment industry.