The "Past Works Characters" or simply "Past Works" (過去の作品) is one of the four sections in the "Logicalism Characters" page in Logicalism. The characters listed in this section is, as the the title suggest, "past works". They're either included in the story "Iro Aseta Tegami", a part of the web comic series "Fushigi no" or "Hinata no" (both currently in private)
Several characters listed here is also available in "Shizuku no", the list includes: