The ending of the main story of Holiday Star is this combined with a massive Tear Jerker, with the characters reaffirming the value of life and their determination to return to the world and move on to whatever future awaits them.
In an extra in Holiday Star, we see Yuuya learning that Sakuya is in danger of being assassinated. We learn that Sakuya really isn't in that much danger, but Yuuya's concern for his little brother is incredibly touching.
Doctor Shuu adopting Miru and Kaku as his own children—not in the "future experiment fodder" sense, either, as when the protagonist catches up to him again he's redecorated his office with Christmas decorations.
Hiyoko's little speech to Yuuya if you choose to meet with him at the temple in Holiday Star