The sensational case of a serial killer, dubbed Japan's "black widow" and accused of killing elderly men — all of whom she met through a matchmaking service — has cast a shadow over a growing trend of elderly Japanese people seeking partners.

The case of 70-year-old Chisako Kakehi — who repeatedly met, dated and married elderly men, including her four victims — came at a time when elderly people have become more and more interested in finding partners amid a rapidly aging population and the spread of nuclear families in the country.

Kakehi was given the death sentence by the Kyoto District Court on Tuesday for the murders of her 75-year-old husband Isao and common-law partners Masanori Honda, 71, and Minoru Hioki, 75, as well as for the attempted murder of her acquaintance Toshiaki Suehiro, 79, by having them drink cyanide between 2007 and 2013.