Yeah, I already looked into this other shit after my last edit and realized my kanji for the name was wrong. I am calling bullshit on this. The "source" is an image, of all things. Written with broken English when Suisei's mother is supposed to be fluent in English. Her Endolu persona has been known for years, so if the best they got is an easily faked facebook message, then I don't believe this horseshit for a second.It was NOT part of the Niconico leaks. Also the idol you dug up there is probably a different person.
I think a fair share of skepticism is warranted, but even so I found the connections are pretty convincing:
Someone unearthed a facebook post from 2015. The post was bragging that their daughter, Julia, had made a CD cover for this Vocaloid album. At the time it leaked to the west you could search for this facebook post and it existed, but as of right now the post is no longer available.
As you can see from the album credits, the person responsible for the CD cover art is Endolu. Endolu has long been associated with Suisei as her past username.
On the mom's facebook, you could find pictures and videos of her daughers Julia Watanabe and Martha Watanabe. These pictures and other pictures on there lined up with previous pictures rumored to be connected to Suisei, where the identity of the people in the pictures was mistaken for Suisei (eg. pictures of other workers or guests at the family restaurant).
If taken at face value, this strongly indicates Endolu = Julia.
The corroborating evidence from the BMI music site where Juria Watanabe is credited for Suisei songs wouldn't really be evidence on its own, especially since BMI can be easily manipulated (anyone can pay to add something), but it doesn't discount the Julia/Juria = Endolu connection.
Now, people who call into question this dox have sometimes questioned the Suisei = Endolu connection. Many of the sources of this connection have been lost, I believe the main one was a game dev who had worked with Endolu pointed out similarities between art Kanata was using (which had been credited to Suisei) and Endolu's art style. I am led to understand there may have also been art connections between Suisei's very early covers as an indie and Endolu.
Nevertheless Suisei = Endolu has been generally accepted since 2020, and I don't really see how the rest is a gayop, but judge it as you will.
Nijifags have been trying to take down Suisei for a while now and that is what this smells like, too.