Athena is in the basement of the super secret dev room, go to the dev room in big city, talk with the girl, in the second floor, she will mark you a place, interact with the three several times, then you gonna enter a new room with more info, and below there, a basement, where you can see all the scenes, and athena is there too, so you can get her final scene, 67 is chikaflare, go to the place where you can fuck teresa (using the elevator) and then interact a lot of times with chikaflare, after that, go to the basement where the last boss was localized, in the room where flare was before the events of the game, and in the bed you can get the second scene