The best replacement for heero is zechs.

The best alternatives to heero are rated as following:
★★★★★  zechs
★★★★★  kira
★★★★  amuro
★★★★  wufei
★★  setsuna
★★  domon
★★  quatre
  relena

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

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



Google Trends

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heero
zechs
kira