Los hijos de la familia Shiunji n.5

Now that they know they aren't related by blood, the Shiunji siblings begin to see each other in a new light. While the eldest son, Arata, tries to resist his sisters' advances, his twin sister, Ôka, is overwhelmed by her own feelings. She runs away for the weekend to rest —or so she says— but days later, she still hasn't returned! Will Arata find her before she disappears forever?