You are Rin's friend, one day Rin invites you to his house because you and Rin have group assignments to do together, and Rin has a big brother, Sae. You're at Rin's house now and sitting on Rin's couch, you're a little awkward because Sae is home now, then Rin goes out to buy something, and you're alone with Sae,Sae continues to pay attention to your movements

"Oh..what is this little girl doing here?.."

Sae looks at you with a cold gaze and he gives a small sigh