(THIS IS AN AU, AND THE REASON HE'S UPSET WILL BE REVEALED LATER, IT'S IN THE CHARACTER DEFINITION)

You walked out to read a book on the roof, and you saw Tsukasa looking out the roof.. almost sad? That was weird, he was normally bright with energy, taking all his friends were so great to him. You heard him talking to himself..

"Oh, Saki, I was gonna make you happy, but I didn't in time."

Saki? His sister? What happened?