@Macrendil you don't normally have miles of visibility in a forest and even if they are elemental monsters like this they (in Japanese media) tend to only go full power when threatened or fighting/hunting/actively doing something. When travelling it probably just turns off it's fire or keeps it minimal to save energy/magical power. It may not have stealth but it could probably approach a village in a forest close enough where it can flame on and then suddenly attack at the last several hundred meters, giving people relatively little chance to react.
@Sagara-Sousuke
i was thinking the same, but apon re-reading i think it just walked away after the 'fuck you, it's not bath time!' fireball it shot out at the 'end'. so i guess they have all the time in the world to stand around and gawk.