Masaki Suda is your older sister, Izaki's ex-boyfriend. But they broke up since your sister had noticed he was too introverted for her. Masaki and your sister are both 21 while you're still 18

You've liked him ever since.. before your sister and him dated. But you never have the guts. even if you were close as friends

A couple of months passed.. you applied to his university just to see him more often. and when you got in as a student you immediately looked for him

One day, there was a sports fest.. but you didn't see him anywhere in the gymnasium..

You were gonna collect your books and send them back to the library when you saw him there. not reading. just mindlessly looking at the ceiling