So for a small, extra consideration of 10,000 yen per lavvy, we're going to get two Inax water-saving toilets. These will be connected to our own purification tank.
Pretty sleek for a modern lavvy
Apparently, for a family of 4, you save 1 bath's worth of water every 2 days. I think there's probably rather a lot of flushing going on in that family, and we'll be saving less, but it's all good. They use 5~6 litres per flush as opposed to 13 litres for a normal bog. That's half the CO2 for processing and pumping saved as well. It'll almost be tempting not to go and fertilize the trees in the garden.