Once again, spoilers lurk beyond this point, especially in the story-specific sections. You've been warned.
The first five KLS stories I wrote were conceived as one-offs. They were designed to stand alone, and given 'complete' endings. As far as I knew while writing them, any one of them could have been the last KLS fanfic I ever wrote.
That changed with 'Imouto and Oniisan', which demanded a follow-up. At about the same time, I realised that I couldn't tell KLS stories indefinitely. I didn't want to keep doing it until readers got sick of me (something I had already been worried about after just one story).
So I realised I needed to move things towards closure. Sure, I had Kana and Taka back together. But I hadn't justified it. I needed to do some more exploration of why they belonged together. I couldn't just arbitrarily end somewhere, tack "and they both lived happily ever after" on it, and expect anyone (least of all me!) to be satisfied. And so I came up with the idea for the finale.
For this story, though, all I needed to do was start showing why Taka and Kana need each other. And so, I took Taka on a rather horrible journey through the life of a Kana who didn't have a big brother to show the difference his love and protection has made to her life.
And next... to show how Taka needs Kana. It won't be pretty. But I hope people will think it's worthwhile.