It's Honoka idea to make the searching "game", but too delusional and naive to know people are monsters if they could have ability to grant their wishes.
Because although we're altruistic, deep down we're capable to limitless horrors if given a chance.
If only Honoka wouldn't suggest that for the coin the Alien would grant any wish, everything wouldn't end up messed up as it is...
Taguchi survived the poisonous fumes from the fire, but seeking revenge after Madoka seems unreasonable as all who was in the group would either join or die, that's more toxic than the plant that killed him.