It's art from the officially licensed GBA port

EDIT: This was also used as the title screen, good and proper Tsukihistory lol

Instead of calling Rinne Tsukihime an officially licensed GBA port, it sounds more accurately it's a licensed converter released during winter comiket 2001. It's software that will convert the PC game into a rom for the GBA. It's expected that one owns the original game to be able to use this.

GreyOmega said:

Instead of calling Rinne Tsukihime an officially licensed GBA port, it sounds more accurately it's a licensed converter released during winter comiket 2001. It's software that will convert the PC game into a rom for the GBA. It's expected that one owns the original game to be able to use this.

Aye, called it a “port” as shorthand.