Shinpei had a very close relation with Kaori and at somepoint Kaori acted as Shinpei's surrogate sister, such as helping Shinpei doing his homework, going together to amusement park and even sharing each other about their feelings and thought.
Shinpei and Kaori shared a strong connection, with Kaori often acting as a supportive figure for Shinpei, helping him with schoolwork, accompanying him on outings like amusement parks, and offering emotional support through open communication.