"Sanzen-sekai no karasu wo koroshi, nushi to asane gam shitemitai" (translated as "I'd kill all the crows in the world to sleep with you in the morning") is an old song sung at a red-light district in the mid-1800s by one guest: Takasugi Shinsaku, a central figure of the early Meiji Restoration who lived a turbulent life. The saying means, "When a crow cries, I must leave this place. Even if I must kill crows all over the world, I want to stay with you a little while longer." The song expresses his longing for amorous time to be prolonged for even just a short while.
In the game Sanzen Sekai: I'd kill all the crows in the world to be with you a little longer, now titled Crows Overkill in its newest edition, players roleplay guests in a red-light district. Many birds gather in front of each player. The players must kill or move birds to prevent them from crying. If birds in front of a player cry, that player must leave the red-light district to go home (i.e. drop out of the game). The player who manages to stay in the red-light district for the longest time wins.