Heiankyo Alien sounds so deeply mysterious, and the cover art on the cassette version just stokes the flames of the mystery. But in reality, this is just Alien, or sometimes Super Alien, the same game as released on the VIC-20 in the western world. This was released on many platforms by a variety of companies, usually with a simpler name, and I believe most famously by I/O. There is a good chance this was just based on or totally copied from magazine source code. I picked this game up with Snake, which I got as part of a small lot of software on cassette for the VIC-1001. It is really quite unusual to find tape-based software for the VIC-1001.

Anyway, as you can see, under the hood we have Alien.

But the cover art *is* cool!