[Lightning is arguably the most important person in her world, so it's only understandable really. So while they're both independent people it'll likely be a long while before they get tired of having each other close. That is if they ever get tired of it.]

[Which is probably why Serah shifts a little once Lightning sits down so that she can lightly lean against her sister as she watches Mog play around in the water.]

So that's how you do it. It sounds complicated, bur I'll give it a try.