>>8691310
Whichever way you mean it, I don't think there is a tag.
If you mean "one girl getting spitroasted/DPd while the other girl only supports from the sidelines," this appears to be quite rare. You can narrow down searches on boorus with tags like assisted_sex and sexual_coaching.
Example:
https://gelbooru.com/index.php?page=post&s=view&id=6870623
If you mean "omemeo but one of the girls is clearly only there to support her friend through the experience," this also seems quite rare. You'll have to pick through stuff manually. You could go based on character expressions, but it'll probably help to be able to read Japanese. Even then, there's further nuance to be found.
For example, in this one:
https://www.pixiv.net/en/artworks/131179144
The one on the left seems to have convinced the other one to join her begrudgingly because "We can earn money and feel good while doing it, it's a win-win."
In this one:
https://www.pixiv.net/en/artworks/121050089
Based on body language, you could potentially interpret this one to be that the one on the left is providing moral support to the one on the right.
I've also found a similar tag called 鞘合わせ, which would translate to something like "sheaths joint/facing." This seems to be a subset of omemeo where the girls are face-to-face, often kissing.
Without a dedicated tag, you'll have to sort through broader tags manually, or try to combine tags to narrow down on the content you're looking for. Since it's very context-dependent, it will likely be very difficult to narrow it down with tags, though.
