in Feudal japan streets used to be illumited by the light of laterns, since if it didnt it would be actually impossible to see, electricity hasnt been invented yet.
i propose nights on ikou were darker, making it harder to see, and put some torches around the city to light the place .
not only that if it isnt hard to code, perhaps players could buy lamps to Npc, to actually be able to see in the dark, could also work in caves or dark underground spots such as Geeky previously posted.
As result of the following ikou era would look more realistic and cooler for rpers