When I was recently researching Japanese videotex systems for similarities to CD Graphics, I ran across Captain https://en.wikipedia.org/wiki/Captain_(videotex)

It was somewhat unique in that (at least originally) it only transmitted bitmap graphics, rather than having a hybrid system with some characters in ROM and others dynamically loaded.

1981 publication with specs of the pilot system (PDF): https://hcs64.com/files/Harashima,%20Kumamoto,%20Kitamura%20...