Awwww thank you so much! I also really loved writing the scene of them meeting... just two kids finding comfort in each other, even though growing up is hard

I think Soobin started falling in love with Kai long before he or Kai realized it. Their relationship has been ambiguous, crossing the line of a "normal" friendship, for years. Soobin knew that Kai was special before the engagement, but he didn't think too much about what kind of special relationship they had. It probably began to occur to him around the time he left his previous relationship and began relying on Kai even more, although he didn't put a name to it...... Being married to Kai brought more of those feelings out. Thinking about their relationship as a stable marriage made him very, very happy. Like Kai, he wanted love in whatever form it came in. The reason that he didn't confess sooner is the same as Kai—fear of rejection. In Soobin's case, though, his concerns were more focused around the worry that Kai spent too long thinking of him as a friend to ever see him differently. It just wasn't a possibility in his head. He also knows that Kai is a romantic, and thought that Kai would essentially have a mental block on falling in love while in an arranged marriage lmao. He feels silly in hindsight, but the long-term ambiguity of his feelings didn't help! Before their confessions, he was also very content with being Kai's partner, so he didn't feel a huge sense of urgency to define their relationship (until the pregnancy, of course)

I'm so glad you asked about the title! It's one I'm very fond of. I came up with the idea of including flashbacks early on into the outlining process. The extensive history of sookai's relationship (and their long future together) is very important to the ficus themes, and these flashbacks bridge the gap between their beginnings to their current selves for readers. Sookai shaped each other; they wouldn't be who they are as adults if they didn't meet as children. In a way, their childhood selves are "communicating" with their adult selves. So, the title refers to the practice of putting a letter in a sealed bottle and releasing it to the ocean for someone to find. You don't know where that bottle will end up, or who will find it, or when it will be found, but you send it anyway. You could say that sookai took a similar chance on each other in the beginning!

(also I was listening to jungkook's too sad to dance when I was outlining the fic and that lyric stuck in my head LOL)