The best replacement for koga is iga.

The best alternatives to koga are rated as following:
★★★★★  iga
★★★★★  inuyasha
★★★  sesshomaru
★★  seiya
★  thorn
★  byakuya
★  iga ninja
★  sesshoumaru
  sabrina first
  muramasa
  kouga

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

Other search terms related to koga and their ratings are:
★★★★★ kagome
★ ayame
You have in mind a companion for koga and it is not yet here? Propose!



Google Trends

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koga
iga
inuyasha