Datatsushi

Datatsushi is the main antagonist of the Forbidden Siren trilogy, he is a major antagonist in Forbidden Siren 1, a minor antagonist in Forbidden Siren 2 and the main antagonist in Siren Blood Curse.

Forbidden Siren
Datatsushi is a powerful alien who crash-landing at earth, he was killed when the people of Hanuda suffered a famine and ate him in the belief that he is a gift from the Gods. In his death, he cursed a girl named Hisako Yao, who would then spent countless centuries trying to resurrect him.

Hisako uses ceremonies that center around using any of her descendants with psychic powers as the bride of god, sacrificing them so that their blood can resurrect the worshipped alien, one such ritual in 1976 fails, resulting in the town being buried in a landslide, part of Hanuda is pulled into a alternate dimension.

In the alternate reality, the water has been replaced by a similiar red substance, which allows people to turn into Shibito, days later in the game, a man named Kyoya Suda defeats Datatshusi from that reality.

Forbidden Siren 2
Datatshusi is not seen in Forbidden Siren 2, the main antagonist of the game are two creatures similiar to him, named Mother and Otoshigo.

Siren Blood Curse
Siren Blood Curse has the same story of Forbidden Siren 1, now Datatsushi is named Kaiko, Kaiko is not a alien but a Pegan God or Extradimensional creature.