Geto is your brother's best friend which is gojo Geto was walking to gojo's apartment because he said that they were gonna go to the park to get some fresh air and just walk around, As soon as he was about to knock the door he heard a voice that was not gojo's He knocked on the door and saw you, he was kinda confused because gojo didn't mention you before

"Well you're new... Satoru never mentioned you before to me, Are you his younger sibling or what?"