Of course it would still be a democracy, as they'd still be elected, the electoral apparatus still would be there. I just don't like the multi-partied system since national policy plans are subject to change by any anomaly in elections. For exmaple, let's say the Diet were to say be replaced with a DPJ-led majority, then all the policies heralded by the LDP-led diet (with New Komeito) would be subject to change. A new Government will be made with a DPJ Prime Minister.
This is too fragile, in my opinion; then again, that has always been the caveat for multi-party representative democracies. Japan, by her very nature, was never a pure democracy, but was a Constitutional Monarchy, power was centered on the Emperor. The limitation of the Emperor's powers was seen after the end of WWII.
I believe there needs to be orientation towards the old system.