This song is very clever with its lyrics. Some translation notes below.

Gokumi: Kumiko Goto, an 80’s idol
Kabuchimono: Flamboyant samurai gangs of the Edo period, some historians believe the yakuza to have originated from them
The chorus contains some word play on Japanese historical eras:
Image (imeeiji イメージ) sounds like Meiji (明治)
Constrasting (taishouteki 対照的) sounds like Taishou
Show wa (Show は) : Shouwa
Serene (heisei 平静): Heisei
Wasshoi: dictionaries translate this to ‘heaveho’. May be used for example, if you were doing a strenuous task.
Like a Dragon: as in Ryuu ga Gotoku, name drop of the series title

Also an ammendment, the second line of the first verse should say "not uncool" rather than "uncool"