|Relations||Karen Ichijo (sister)|
Karen is Kosuke's older sister. She has a good relationship with him, which can sometimes appear maternal. Their parents do not appear onscreen so Karen is seen taking care of him. Despite their age gap, they still share a room and bunkbed, with Karen sleeping on the bottom and Kosuke on the top.
Imadori and Kosuke became fast friends due to their shared interest in Hatenko Robo Dozibiron and Imadori's immaturity. They initially met online and eventually got together at Kosuke's house to play Dozibiron.