A small addition to this post about japanese fandom tags
Japanese fandom is very strict about seperating stuff. And there's been plenty of angry posts about mixing Plus and Yume tags (some japanese fans do it too).
Plus (プラス) basically used as "x reader" meaning the viewer of this content can insert themselves in this content. There's either blank character as "you" or some plain design which is easy to project yourself on. It is frowned upon to use non-canon characters in this tag, especially in romantic setting.
Yume (夢) is more personal. Here you can show your original character or sona, which has distinctive features, design, face, character etc. This is just safe space for yumes to share their content.
It doesn't mean that a stranger can't enjoy someone's yume works. But it's not everyone' cup of tea and some strongly dislike or just avoid it (e.g. non-sharing yumes). Sometimes creators even mention if their Yuu has "voice" or "character" or "backstory" because it makes it harder for other people to self-insert in this case.
And many fans ask to respect this and tag appropriately.
Some other details or which words you can mute/use in search
As mentioned above, sometimes seeing another character with your fave can be triggering. So to warn that there's "prefect with face" many people add this note to their post:
etc. Which are translated as "Prefect with face"
Many people prefer specifically fem or male Prefect when paired with certain characters. To indicate this creators usually add ♀️ if it's a girl or ♂️ if it's a boy
For example: セベ監♀️ - Sebek x fem.Prefect
Or add kanji for woman/man: 女監、女監督生
It's important sometimes to mark your posts as "headcanon" in order not to cause confusion, that this is your "delusion" and not canon information.
In this case such worsa are used:
※妄想 (mōsō) - dellusion, fantasy or imagination. Personal headcanons or romantic delusions. Silly and lighthearted.
※捏造 (netsuzō) - fabrication, something made up. Invented details which do not exist in canon. Like made up lore or events, childhood memories not shown in canon, family relationships, etc. Basically anything not covered in canon. Very important tag.
These 2 words are often used together.
Just small addition that came to mind tonight.