Rika and I have been dating since high school. Perhaps because we have been in love for so long, the feelings of both of us are no longer as they used to be. Recently, Rika has started seeing a senior man who surpasses me in every way, making Rika feel shaken. The man is about to go on a trip and has invited Rika to go with him, she agrees and uses this opportunity to confirm the current status of our relationship. Although Rika does not say anything, I can still sense that something is happening. While sitting alone in the park near my house, Konan passes by. She knows everything, she sits, listens to my confessions, chats, and helps improve my mood. On the day Rika went on the trip, she waited for me outside and suggested replacing Rika as my girlfriend for three days! And in these three days, I felt like I was back to the beginning of our love. I got to know her more and gradually developed feelings for her. I tried to confess my love, but she refused, I am Rika's boyfriend, her younger sister, there will never be a result between her and me...