So... is D4 Princess finished or not?
NO, it is not finished.
Why?
The anime finished before the manga:
Anime finished: September 28, 1999
Manga finished: September 18, 2000
MangaUpdates contains information about the anime adaptation and indicates that it is incomplete.
Watching Order (by release date)
Here you have all the anime relations we detected ordered by release date, so you can see the reason for this status in context and also use it as watching order.
The mangas and the non-core contents are excluded by default, but you can enable them by clicking the buttons below:
Synopsis
D4 Princess centers around Doris Ruridou, a young princess starting at Teito Academy.
She's not just any student; she's a Panzer, someone with special abilities who fights with a unique weapon called a "tool".
Doris's life takes a turn when her older sister appears, ready to train her in the ways of Panzer combat, as she'll face challenges from other Panzers.
The anime follows Doris as she learns to control her powers and navigate the world of Panzer battles.