This song is included in this channel's Japanese song playlist
https://www.youtube.com/playlist?list=PLjDc9r7oZzO6NiLl_amQwEDB-EA0ek00g

愛人 (Aijin) meaning "A mistress", won the Grand Prix （グランプリ）in 1985
The other two Grand Prix wins by Teresa Teng were for her 「つぐない」 (Tsugunai) in 1984 and 「時の流れに身をまかせ」(Toki no Nagare ni Mi o Makase) in 1986. This was the first time in Japanese music history that any singer had won the Grand Prix three years in a row.