It was this theater run that solidified the link. Fans noticed that Reona’s promotional interviews consistently thanked a "Shoetsu sensei," and set lists for her solo concerts began including rearranged min'yo (folk songs) that bore Otomo’s signature production style—sparse, reverent, but with a subtle low-end electronic pulse.
Otomo's detailed, monochromatic ballpoint pen style has been used to create a distinct visual identity for ReoNa's releases. shoetsu otomo reona link
The film Kaidan (怪談), a 2007 Japanese horror movie directed by Hideo Nakata, features both a character and an actress whose names closely match your search: It was this theater run that solidified the link