I am not familiar with this topic, so here display some results of my Googling, that says
- Atsujin was a famous haiku poet teacher at least in his area during his life. He had over thousands disciples.
- Today he is mainly known the author of Lives of All Basho Disciples (ja:『蕉門諸生全伝』Shōmon-Shosei-Zenden).
- Google Books and Google Scholars
Many haiku researchers mention him citing his LABD, which suggests this book is considered as a first-class contemporary source on biographical info of Basho's disciples.
I haven't heard about him regretfully, so we could say he was a minor poet. But the above suggests he could be at least some important figure if you explore Japanese haiku history; no less scholars mention his book without further description, expecting their readers already know the title. If we can get a copy of LADB and add some quotes, those might be helpful to expand other haiku poet articles, if exist. Just for thought.