Aliasing mussai002 → 7th
Link to alias

Reason:

Same artist. Pixiv profile.
It's one of those aliases where I don't know what should be aliased to what. First is pixiv id, second one is more used.

Any ideas on where the name 7th even came from for them? I'm not finding it anywhere. I'm guessing it may have come from another booru, but it's not even close to anything they're using now. It's either very old, or it was one of those mistranslation-attempts that sometimes happen and then keep getting passed along through the boorus and boards. At least, that'd be my guess. Probably not going to make mussai002 the main tag because we've gone away from using the pixiv logins, because they're harder to get now, and they were always obscure/not as visible and a makeshift way of handling pixiv artists.

I think we'd be better off aliasing both to their current pixiv display name instead. Their current pixiv display name is nnsn, which looks like it's an abbreviated version of their last pixiv display name: "ななすん" (or "Nanasun"). So we could go with either nnsn or nanasun. Aliasing them all to go to --> nnsn would probably be the simplest and most straightforward. Any thoughts?

Yep, go with nanasun.
7th is yet another mistranslation. (ななつ = seven)

The self-introduction still says "I'm nanasun. Don't have Twitter."

Alright then, aliased nnsn, 7th and mussai002 to --> nanasun.