These characters appeared, not in a manga, but in a pair of best-selling hardcover books, Sekai-no Kaiju (The World of Monsters) and Shin Sekai-no Kaiju (The New World of Monsters), published by Akita Shoten in 1967 and 1971.
The books feature illustrated stories on these original monsters, such as Zagora and Bagun, and are very evocative. Some of these monsters created an impression on those kids who grew up with these books, and is why they have been translated to vinyl.
Currently, I own two mint copies of Zoku Sekai-no Kaiju, which I purchased at a local Japanese bookseller (back in the day) — these are very, very expensive if you manage to find them today.


