The version I have is the Japanese one with the subtitles. Despite Tsuchiya preferring the US one, his character in the Japanese one has some depth, as at one point he goes into a story about how he underwent a radical new treatment for cancer and wound up getting the power to become vaporous.

Looking at this film, I can say that to a degree, the character is sort of on par with Claude Rains "Invisible Man" character. He's drunk with power, delusions of grandeur, and very dangerous. Perhaps the character of The Vapor Man may have been inspired by it somehow.