Hmm… I thought this was dark humor or something for a second but after seeing who posted this I am quite confident it’s just inside joke or something that I don’t get-nya.
Adds context: Yakuza gives flower vase to someone marked for death. (ie: a vase to remember someone after death, which you see in Japanese classrooms to remember students that have passed on during the school year)
Italian equivalent: Mafia also gives fish wrapped in newspaper to someone marked for death. (ie: "sleeping with the fishes")