yup, the tank is actually under the seat, and the area which is occupied by the tank usually is a storage compartment. Possibly the best commuter bike ever, don't have to lug around a helmet everywhere.
I'm guessing Roawn's only interested in feet first scooters (ie, "cruiser scooters"). They are way more comfortable, more stable and come with the same brakes and engines as their crotch rocket siblings. Postie bikes are uncomfortable as sin, as are most crouching scooters.
also, some links:
http://www.freewheel-jp.com/trikes.html
http://www.dragon-japan.net
http://www.showcase-tune.com/index2.html
Honda Fusion clone:
http://www.cfmoto.cn/Product_info.php?id=64