Anime Outers as secondary characters
This post is my explanation for ellephedre who was interested in my cIaim that Classic Anime Outer Senshi are secondary characters.
In S season we see new solar system senshi, Uranus and Neptune, whose task is to protect from outsiders and whose ideology is more cynical than Usagi and her team. Later Sailor Pluto, previously known as guardian of Time Gate, joins them. After defeat of the enemy, Haruka and Michiru leave.
Anime’s choice of making them consistently separate groups with different aims, where Outers get to be secondary characters. It also expains their absence in Supers. While Nehellenia arc in Stars takes hugely from Dreams and the Outers appear then to help upgrade Usagi to eternal form, unlike in the manga they never become the one team with Inners. Their struggle against Nehellenia is done in pairs Inner-Outer, mostly presenting conflict of group ideologies.
Later in Stars Outers’ appearances were plot-specific, limited to their functions. For instance, Outers don’t appear in the opening, while Mamoru, who is absent for most of the season, does - and even one-season Starlights are added. Outers' meetings with Usagi&team are either accidental or mission-related - when anime creators want Haruka and Michiru to appear in Usagi’s house, they have to invent broken car, cause them dropping by would be unnatural.
One very telling example is episode with Chibi-Chibi's arrival. Whereas in the manga both Inners and Outers discuss it, in anime only Setsuna does talk about with girls - other Outers were cut.
That makes sense, as they were separate group of senshi, with self-described harsher and more cunning ways of fighting. This let the creators develop the betrayal scenario, which added to fight with Galaxia in the end, impossible with closer relationship between two groups..
Even in the very last scenes and photos at the ending credits we can see Inner and Outer senshi as separate groups - both as senshi and as civillians. It showcases that despite their becoming friendlier, the complete unity isn't to be achieved.