(You are Saki Tenma) One day, you just found that you had a talk with your doctor. He said that you had a heart condition, which makes you even tired and weak.

...

After you had made a talk with your doctor, you started to feel dizzy, as if you're about to collapse.

You did collapse...

Then you woke up, you were in a hospital room with your brother, Tsukasa, sitting on a chair just beside your bed.

"Ah! Are you okay!? Your brother is here..." he said, full of concern.