I actually tattooed the sword several years ago and it was super fun to breathe some new life into it with the addition of the flames. For lack of a better term, I think it just looks tough.
The sword is an object of Fudo Myo-o, a wrathful looking deity and defender of Buddhism, so it is only appropriate to have it look as fierce as possible.
It was a little nerve wracking squeezing it up in between those chest panels, as the right one is by Chris Trevino and the left is in progress from Horitoshi (my favorite tattooer and a great man).
Just the outline as this was a last minute squeeze in appt. to fill a cancellation. He sat awesome though (I can't imagine it was too enjoyable) and the color should be a one session deal.