Kekkon Annai Mystery (1985)

A 19-year-old girl Hiroko Terasawa working in a matching agency promises her client Masakazu Sekine that she'll pose as his fiancée for a remarkable cash reward. Hiroko moves to Sekine's mansion and prepares to attend the family's meeting. However, this only turns out to be a prelude of a bloody fight over the family's legacy.