If you are travelling between Tokyo and Osaka (or Kyoto), but wish to save transportation and accommodation expense, overnight coach service is the best way for that.
For example, single ticket by Shinkansen between Tokyo-Osaka costs approx. 14,000yen, while sleeper coach (depending on type of vehicle though) costs 5,000-8,000yen/one-way.
Duration is around 8hours ( departing around 10-11pm = arriving 6-7am) with rest stop en-route. Most vehicle are equipped with rest room and complimentary wifi service. Female solo traveller may opt for “Women-only” seat available on selected coaches.
Search & book the coach : www.kosokubus.com/en/