Sleeping in Japan can quite often be an expensive thing and unlike the USA where hotels charge per room, in Japan it is often a price per person. I am going to run through a couple different options that are decent, cheaper alternatives to regular hotels in Japan. See other places to stay.
Love Hotels are quite interesting and unique to Japan. Basically, love hotels are for couples to spend a few hours alone together as walls in Japanese homes are (sometimes literally) paper thin. Love hotels tend to have larger rooms than regular hotels, with nicer (and larger) bathrooms, plasma tvs, karaoke, video games, and access to dvds (adult and regular movies). Rooms can have various types of themes and some have various “amenities” such as massage chairs, slot machines, saunas or even a small indoor pool. Some hotels have different themes per room and other hotels have a theme for the entire hotel. There are two options, rest (2-3 hours) or starting from around 10pm you can stay (9-12 hours). Prices and times vary depending on the place, time of day, and if it is a weekend/holiday. A typical love hotel will cost about 3000-5000 yen for a rest and 7000-over 10000 yen for a stay. Often you choose your room by pressing a button next to a picture and then pay a person behind a opaque counter (privacy is important here). Apparently they will not let more than two people in a room nor do most let same sex couples in (sometimes).