This is how I believe a Remus a Sirius got together and it does go up until book 7. Which means there is book moments too.
Year 1
James, Sirius and Peter all become フレンズ at the start of term feast. (Well actually just Peter becomes they're friend but あなた get the point.) Remus doesn't befriend them until later that 年 but he is already フレンズ with Lily. When they do become フレンズ Remus is instantly チャームド〜魔女3姉妹〜 によって Sirius.
Year 2
(Near end of year) James, Sirius and Peter find out about Remus' condition. Which of course we know that they still want to be his friend.
Year 4
Remus stars to develop...