The timeline goes something like this:
Ages unknown (5000 BC?). The Juunimoun sprouts, Yomiki village is found on sacred grounds.
Tendou, Maeda and Shinohara families are established. Tendou family makes contact with the Maiden of the dead with the Guarduian Spirit's blessing. (?!) That is quite a 'blessing'.
1000 AD. Kimura family is established.
1800s. The families shift their roles. Sakaguchi family moves to Kyoto, though they still visit Yomiki occasionally.
1880s. Sakaguchi Kuroki is granted the title of Baron, travels across Europe, finds a rare occult book.
1888. Sakaguchi Kuroki returns from Europe, builds the mansion. (Why did he kill the workers?)
1889. Sakaguchi Kuroki marries Tendou Shizune
1891. Eina and Mina Sakaguchi are born. Shizuin moves in the Mansion. Yukina's mother is hired for help.
1900 - Shizune dies in mysterious circumstances. The Baron goes lethargic for a month, then goes mad.
1903? - people start disappearing, then the incident happens. Shizuin and Mina are the only survivors. Shizuin is a likely accomplice (presumably in an attempt to get her sister back), goes mad from the experience. (Why Mina? Were there any people missing?)
Larger consequences are unknown.
1907 - Sakaguchi Maruo moves in with his family.
1908 - Sakaguchi Michuru, Maruo's daughter hangs herself. Maruo goes on a rampage in an attempt to perform yet another ritual. (When did his mother fall into a well? Did the mansion burn down?)
Nothing important seemingly comes out of this unless we missed it.
1917 - Maeda Keiji is born. (Who are the parents?)
1908-1937? - Maeda family rises to prominence. (How? Did Yukina marry? Was it her brother?)
1937-1945? - The Ward169 chapter. Experimenting on children. Maeda Keiji gets his degree in pedoatrics.
Somehow, the German gold is buried in the Ward and does not feature in the plot again until the present day.
(What was that flashback of two people talking how Adachi told them about the gold - they don't sound like Tokigawa and Sawada. Who are they? Was the good doc not the first one lured here? For what purpose?)
1950s - Shinohara Juuzo is born.
1953 - Kayano Kagusa is born.
1966 - Kaimei hospital is founded in the place of Ward169. (A coincidence? Was the land so good that it couldn't have been left alone? Or was it a conscious decision by Maeda Keiji to become a director there? Was he drawn to it?)
1970s? - Shinohara Madoka is born. (When exactly?)
1974 - Kayano Kagusa is hired. Transferred to a paediatrics ward.
1975 - Kayano Kagusa talks to a patient and has a breakdown, presumably due to discovering Keiji's antics. Is transferred to a psychiatric ward.
1976 - a high-profile murder case occurs, prompting a series of fatal accidents and disappearances. (Sachiko Nakajima's case. Could be that it was always the same, but anything before went unreported? We never found about its significance)
1975-1979? - Kayano Rina is born. (In captivity? Is Juuzo the father? Why did Kagusa call him a betrayer?)
1979 - Kayano Kagusa is terminated in February. In April, Maeda Keiji sets fire to the paediatrics ward after chaining the exit, then goes missing. The hospital is closed down in May. (Why did she become the pool ghost? Why is she so powerful? Did Juuzo kill her? Who is the author of the note we found in a locker?)
1990? - Maeda Nami is born.
1992? - Shinohara Seiji is born. (Who is the father? Is it important?)
1997? - Tendou Shizuka and Seika are born.
2000s? - Shinohara Madoka dies. (What are the circumstances, any relation with the curse of the land?)
2004 - Maeda family declines, Uehara's mother gets exiled after a failed cleansing ritual attempt, Shinohara Seiji 'dies' saving Maeda Nami. (Are any of those connected?)
2010 - IAE and Kaimei join forces due to Dr. Bryan Cooper's discovery. Ikei is rebuilt for that purpose. Foreign intelligence takes keen interest in the Project. (What is the Project?)
2010-2012? - OMOIKANE Project? The birth of Shinoseki Adachi, or 'Shinohara Seiji'? (Doubt it was before 2010. What would the files do in Ikei if they were from a project undertaken before its construction? Yet Sawada indicates that 'Seiji' attended a university with him, meaning they go way back. So when did it happen, exactly?)
2012 - 'Shinohara Seiji' and Seika meet, fall in love. The Project test run happens. Everything goes FUBAR. Seiji preserves Seika, but is marked for death. He still manages to give Sawada his notes. (What happens to Seiji? Is he replaced by yet another copy? Who is the man in the hospital Uehara saw?)
2010-2014? - Kana Akio dies in the hospital in unknown circumstances. (What was her connection to the plot? What could we do for her or her father?)
2014 - Shinohara Juuzo plans to lauch another experiment related to the Project that has to do something with Mitsuki, but Seiji beats him to it and launches his own. Mass murder ensues as 12 people go missing while the rest simply die.
Anyone remembers any noteworthy events that are missing?
What were Seiji's goals, reuniting the realms? Was it in accordance to the goals of Maiden of the Dead? What happened to Kozaka, Shiba, Murano etc? How did Juuzo end up with us, was he alive in a sense that the 12 were alive? What determines if you are one of the 12 or not? Was he trying to wrestle control to stop Seiji, or did he have another goal in mind? What was supposed to be Mitsuki's role?
Was a streak of disappearances that Mori was investigating connected to the Project, or was it due to the curse in general?
Who was that 'she' Juuzo saw during the end of 3rd night?
While I have the timeline, I am still fuzzy about the major characters' motives, and most of the occult stuff is incomprehensible to me.