Becoming Part of the Family

Becoming Part of the Family is a harem ending and one of 12 possible third chapters in Shiny Days.

Plot
The plot of Becoming Part of the Family follows the upper branch storyline up to the point where Karen confesses to Makoto. Makoto asks if Karen isn't confusing admiration for love, and she insists that she loves him. He hesitates, and says that he's supposed to walk around the festival with Setsuna. He starts to leave, but Karen jumps on him, knocking him down. She then points out that Setsuna has already left, and Makoto infers that Setsuna must not have liked him after all.

Karen asks if she isn't good enough for him, but Makoto replies that maybe it's him that isn't good enough for her. Karen disagrees and kisses him, and they have sex in the feast hall. Just as they're finishing, people start to wander in for the ceremonial feast, including Otome. In a panic, Makoto and Karen hide behind the children's shrine. One of the youth association men points out that Makoto was supposed to have fixed the shrine, but it looks worse now than before. Otome goes to inspect the shrine, wondering why it's still broken if Makoto was working on it.

Karen suggests they have sex again, but Makoto is hesitant with the room full of people they know and Otome standing just on the other side of the shrine. Karen kisses him and convinces him, but freezes when she sees that Otome has walked around back and is staring at them, tears in her eyes.

Otome breaks down crying and accuses Karen of stealing Makoto from her. Makoto doesn't understand, and Karen says he must be really slow to not have figured out by now that Otome likes him. She quickly devises a plan and whispers it to Makoto. He tells Otome that he likes her, and he never said anything because he didn't think she liked him. Otome is suspicious of his claim, and asks why he's with Karen if that's the case. Karen explains that because they're sisters, they so similar that he likes them both for the same reasons.

Otome seems hesitant to accept their story until Karen simply shrugs and says she'll keep Makoto for herself then. Otome backpedals, and Karen suggests that she and Makoto should have sex. The last of Otome's hesitation evaporates, and the three of them have sex behind the shrine. As they're finishing, Otome accidentally grabs the tablecloth under the shrine and knocks the whole thing over, revealing themselves to the entire room.

In a picture shown after the credits, it's implied that Makoto received a beating from the rest of the Katou family, but ultimately was allowed to continue seeing Otome and Karen.

Route
The route to Becoming Part of the Family follows the upper branch for chapter 3 stemming from the chapter 2 episode Part-time Job.

The only requirement for this episode is that the bar be sufficiently low by the time Karen confesses to Makoto. Decisions made during the chapter don't seem to have an impact on the route. As such, this ending is similar to chapter 2's No More Tears to Cry, in that it establishes a minimum bar threshold that must be met to proceed further in the chapter.

The one catch to getting Becoming Part of the Family is that the bar must be just high enough to avoid the ending Lending out Makoto earlier in the chapter, which also has a low bar threshold requirement.

If the bar is too high by the time Karen confesses, you will get the episode Fruition instead.

Determining exactly where the bar thresholds are that differentiate Lending out Makoto, Becoming Part of the Family, and Fruition is difficult, so some experimentation may be needed to get the desired episode.