It's one of those Japanese thingies on which part of the sewer water and the rain water fall on and flow toward the main sewers, if Yu's feel inside, well, they would melt and stuff.
I'm not sure about the Marisa, but the Koreimu is doomed for sure if nobody tells them about the huge gap.
A WALK 2
In the street, cars are dangerous, ze
Walk on the edge of the street, ze
[We're] very easy, ze