Karin to.

Overview

Oosawa Junpei is what people considered a loser - an astronomy geek with bad grades and terrible at sports. Although it seems impossible, he is working around trying to get together with Kido Karin - his longtime crush. Unfortunately for him, Karin has a perfect twin brother, someone who's in the Junior Japanese soccer league, gets top grades and of course, is good looking. Then just out of nowhere, when Karin asks Junpei to go to the planetarium with him, Junpei is caught peeping into Karin's room with the telescope when she's changing by Karin's twin brother. He is then brought up to the roof where there is an alchemy circle drawn... (Source: The Waffle House)

Source: AniList