"Sawatari" seems to be "沢渡" romanized so I used that to make sawatari_(user_kpxt5777) with stacc as the qualifier since we have a character tag with a similar surname (sawatari_makoto).
In the future, you can also just use the stacc name if the artist doesn't have any other social media account to use for a name instead. Making an artist entry with a Pixiv name that can't be made into a valid tag will usually default it to the stacc name instead.
