It's a Josei-ish manga in which Kierkegaard has been reincarnated into contemporary Japan and decides to become a musician to communicate his philosophy to people. It features other reincarnations, notably John Locke, who makes my skin crawl because he's of course the father of liberalism, but his role in the story is positive enough.

Mostly I just like the portrait of Kierkegaard and the silly references (and the author does include citations!). Also it's just something different from most of what you get, even if Kierkegaard in many ways ends up playing the typical Josei male lead.

Also disclaimer: It takes like four chapters before he switches to electric guitars, so it's not really "Unplugged". I think he plays an acoustic guitar publicly only a single time.