Third season of Ai Mai Mii.

Second season of Ai Mai Mii.

It's in the not too distant future. One day Nuku-Nuku dropped in and began to live with the Natsume family. Having lost her memory, Nuku-Nuku assumed the identity of a beautiful girl named Atsuko Higuchi. She was so beautiful and gentle, and besides, she was such a great cook that Ryunosuke, 14, was all smiles. However, after her arrival in town, a series of mysterious incidents started to happen in Maneki City - Experimental machines running haywire, roaring fighter aircraft flying low, mass destruction in the city. In every case, a mysterious girl was spotted at the scene of the incident. (Source: AnimeNfo)

In most ordinary high schools, many stories and rumors float around—some scandalous, some happy and some...more macabre. One such example is of monsters lurking in an abandoned mansion outside of town. Such tales, however, prove too tempting to resist for Hiroshi and his friends Mika, Takeshi, and Takurou. They decide to brave the rumored dangers in order to investigate the manor and complete a test of courage. Each of them approaches the mansion with an overwhelming sense of dread. And when they enter, they come upon a blue monster named Ao Oni who attacks them. As Hiroshi and his friends try to solve the various puzzles in the mansion and escape their new blue nemesis, they find themselves meeting several horrible endings as they fail miserably. [Written by MAL Rewrite]