I purchased these from Sei Gotō (https://x.com/gotosey) at the end of last year. Many of these works document their Comiket and doujinshi activities before they took off towards commercial manga and illustration. Each one is signed and others that aren't by Sey were included in the sale. Other artists are strictly from the circle O2-Club and comprise of Aoi Mitsuya, Kuno Aoi and Ozaki Yoshimi.
Given the time period these were made, its a great record of what became of the fujo doujinshi community by late 1985 onward as the Aniparo boom slowly faded out and was replaced by artists who created original works with more fervency. Sei created several Saint Seiya and Captain Tsubasa works, so I'm very happy that she sold these to me.
Additional artists from the sketches sold are Mitsutani Aoi (Mitsuya Aoi / 三津谷葵), Kuno Aoi (Sometimes Hisano Aoi / 久野蒼) and Yoshimi Ozaki (尾崎芳美), who actually headed O2-Club. This is an image set as these works are not aligned in a book or CG and are loose works / drawings / fliers from a span of 3 years.