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Sakuga atwiki says this is Oohashi, but no source is given.
https://w.atwiki.jp/sakuga/pages/991.html
Axiom said:
Sakuga atwiki says this is Oohashi, but no source is given.
https://w.atwiki.jp/sakuga/pages/991.html
I feel like it's decently safe to tag him (with the presumed tag, of course) as this OP is in many ways very similar to his Takarajima one (post #24100)
※オープニングは大橋学の仕事ではありません
https://www.maocloud.net/works/

I think this might be Sugino's work.