Sequel to "Why James Potter's Sister Isn't a Girl." This is what happens when Al and James get to the Astronomy Tower and their brokenhearted sister. Brother/sister fluff, and you don't have to read WJPSIAG to understand this one, not really.

When Hugo walked up to James at the breakfast table on the morning of the biggest date of his life, James is forced to make a choice between the girl of his dreams and someone who, to him, isn't quite a real girl at all-his sister.

We know "Snape's Worst Memory," but he wasn't the only one that lost a best friend that day. This is that day at the lake, from the POV of the other person whose life changed that day-Lily Evans.