Crystal Monsters (1987 magazine)

Crystal Monsters Monsters (Japanese: クリスタルモンスター Crystal Monsters) was Maruko Jinko's early design concept of Crystal Jewels, first proposed to Demogames from early 1987 through August 1990.

When he came up with "Crystal Monsters", as a reference of his hobby and animal researching, and he imagines "one gem into another", the title "Crystal Monsters" turned into "Crystal Jewels".

Various Crystal Monsters are known or believed to have originated from this early concept work. Each of the issues were written and illustrated by Maruko Jinko and each represents the concept of the Crystal Jewels video games. When Jinko stopped doing the magazines, he decided to rename the game. The video game development has officially begun in 1990.

Concept
In the second book, there is one image. It's some sort of poster/ad design. Turns out, the development really begin in late 1986 & it was then called "Crystal Monsters"

It looks like development started in the Winter of 1987 & was scheduled to be released in February of 1988. From what I can tell, there was not enough funds to continue development so, "Crystal Monsters" was put on hold in early 1988.

The surprising success of that game helped to give Gameguys the resources that it needed. In 1989, it was put to an internal vote as to whether Gameguys should complete the Crystal Jewels games (then still called Crystal Monsters). 80% were for finishing development. In the summer of 1990, "Crystal Jewels" resumed development. While development has started once more, numerous interruptions (all money related) kept popping up. And as such, they developed many other games while still working on the game.