Jiro Hitoyoshi's character is a throwback to Jiro, the main protagonist of Kikaider. Not only do they share names, but in episode 3, he's seen playing an acoustic guitar, which is what Jiro from Kikaider is always seen carrying on his back. Jiro Hitoyoshi is also seen playing guitar on the album cover of Concrete Revolutio's soundtrack.
There's a scene of Kikko eating toast only in her undergarments early on in the series. This is actually a call back to creator Shou Aikawa's earlier work, Neo Ranga. Which has a similar scene involving Yuuhi eating toast in her undergarments.