The best replacement for japanese is chinese.

The best alternatives to japanese are rated as following:
★★★★★  chinese
★★★  korean
★★★  american culture
★★  american cars
★★  chinese language
★  german cars
★  chinese culture
★  chinese green tea
★  french
★  german knives
★  spanish
★  mandarin
★  chinese characters
★  german
  chinese game
  brazilian hair straightening
  swiss movement
  chinese food
  chinese martial arts
  chinese dragons
  chinese writing
  american business culture
  chinese harder
  chinese girls
  korean language
  chinese easier
  european cars
  korean harder
  chinese eyes
  chinese wisteria
  brazilian straightening
  swiss watches
  chinese dragon
  chinese symbols
  chinese facial features
  american akita
  chinese navy
  chinese easier to learn
  american baseball
  chinese art
  american business
  korean guys
  korean girls

Your alternative for japanese is not listed? Suggest!
Speaking about japanese, one probably shouldn't forget about ease.

Other search terms related to japanese and their ratings are:

★★★★★ ease
★★★ conscious thought
You have in mind a companion for japanese and it is not yet here? Propose!

Google Trends

Scale is based on the average worldwide traffic of japanese in all years. Click on graph for more.