Tenchi Muyou! Manatsu no Eve

Tenchi's household is thrown into chaos when a teenage girl named Mayuka suddenly appears and calls him her father. Washuu's tests confirm an impossible result: Mayuka truly carries Tenchi's blood, suggesting that she has somehow come from a future that should not yet exist.

While most of the family tries to welcome her, Ryouko senses that something about Mayuka is wrong. Her suspicion points toward a hidden force using the lonely girl for its own purpose, placing Tenchi and everyone around him in the path of a threat born from darkness and twisted affection.