Interesting that Masafumi Ogata is credited here as オガタマサシ. He's occasionally referred as Masashi Ogata elsewhere such as RISTAR and the English website for Rez, but I think this is the only time it's done in katakana. Doubly interesting since OLIO2 released the same year as RISTAR.
Also T. Segawa (maybe
Takaya Segawa?) illustrating for Saeko Sasaki's track does make it more plausible that she and Saeko Segawa are the same person. EDIT: The commentary for Saeko Sasaki's song in the first OLIO confirm it's Takaya Segawa.