Tenchi Muyô! Manatsu no Eve

One hot summer day, a young girl suddenly appears in front of Tenchi claming the he's her papa! Everyone wonders who the mother could be, and this greatly upsets Ryoko, and she wants the new rival to leave. Lurking in the background, Yuzuha, the Demon of the World of Darkness, is about to get her revenge! So it begins, Tenchi must fight for his friends and Mayuka, daughter or not! (imdb)