Adult PC Game: Miko Kui -Mashu no Kuro Hako- by Valkyria Archive

For the girl he once knew, for his own revenge, Akitaka opens pandora's box, and unleashes tentacle hell. Akitaka has lost his memories. He reunites with Tsubasa for the first time since their ch*ldhood, and calls on the power of "Mago" to restore his mind... while Mago's instinct is to attack shrine maidens!

In all the chaos, Akitaka can't tell if the memories that have returned are real or not.
"You were deceived by the shrine maidens. Don't listen to the lies."
"Oniichan. Don't you remember me?"
Voices in his head grow stronger and his reasoning begins to crumble. What is true, and what's a lie? In the end, you must decide!

And once you do... will it be salvation, or an abyss of despair...!?
Witness the shocking conclusion for yourself!!