Captivated by the Twins

Captivated by the Twins is a Nijou Kazuha/Futaba ending and one of 12 possible third episodes in Shiny Days.

Plot
Captivated by the Twins follows the orange variant of the lower branch plot up to the night of the festival, the plot is identical to Double the Pleasure.

On the day of the festival, Makoto notices that he has a missed call from Karen and calls her back. The call is picked up by Futaba, however, as Karen is in the restroom at the time.

Futaba enacts a scheme for her and Kazuha to seduce Makoto. They go to his apartment to seduce him, and the three of them end up having sex for the rest of the evening. Kotonoha, Kokoro, and Setsuna are left waiting for him on the train platform. When he doesn't show up, they decide to abandon the festival and go home.

Route
Captivated by the Twins follows the orange variant of the lower branch. It shares a node in the route map with Banquet of Mothers.

The key to getting Captivated by the Twins is to not seduce Manami during Makoto's late night visit to the Radish (it does not appear to matter if he seduces Mai or not).

Then, on the day of the festival, whether or not Makoto decides to return Karen's call comes down to the state of the bar. If the bar is low enough, he will return Karen's call and begin the chain of events that leads to Captivated by the Twins.

If chapter 2 being Drowning in Secrets and chapter 3 follows the green variant, these events will also happen.

If the bar is sufficiently low, but Manami was previously seduced, the ending will be Banquet of Mothers instead.

If the bar is too high, Makoto will decline to return Karen's call. As a result, he will end up going to the festival, yielding either 33322 or Stubborn Makoto instead.

There are two variants of Captivated by the Twins. They are based on whether or not Makoto guessed "Kazuha?" when Futaba answered Karen's phone. There are scene and dialogue differences between the two variants, but do not change the route or ending. Some reports indicate that the route map node may not be filled in until you have completed both Captivated by the Twins and Banquet of Mothers.
 * If Makoto guessed that Kazuha had answered the phone, then Futaba gets the impression that Makoto is in love with Kazuha, and her plan involves setting them up as boyfriend and girlfriend (but to also share him for sexual purposes).
 * If Makoto did not guess "Kazuha?" on the phone, then Futaba's plan is simply for her and Kazuha to share a relationship with Makoto.