On 18 Dec 2009, there are 2 types of the train services that runs from Otsuki to Kawaguchiko, namely the Fuji Exp and Fujisan Ltd Exp.

I know we have to pay extra for Fujisan Ltd Exp and thus I limit my choices to Fuji Exp which charges 1110 JPY.

At 1307hr, the fare for Fuji Exp19 is 1110 JPY.

But at 1335hr, the train service is still Fuji Exp but there is an additional fee called Order Ticket of 200 JPY.

What is this Order Ticket fee about?

Of course, it is not random. It always appears when it is not a regular train but a "Fuji Tozan" train. The same explanation applies as above.

The following page shows train departures from Otsuki:
http://www.fujikyu-railway.jp/forms/info/info.aspx?info_id=13108

Yes, all seats on the regular trains and Thomas trains are unreserved. And half of the seats on the "Fuji Tozan" trains are unreserved.

If the train is crowded, does this mean we have to stand all the way?

Fuji Tozan train (colored grey on the timetable):
http://www.fujikyu-railway.jp/forms/info/info.aspx?info_id=12932