Aoyama Haru and Kagaya Kaede have been friends since they were 4 years old, when they began living next door to each other. They are now 24-years-old and still live in the same apartments. Kagaya Kaede has held feelings for Aoyama Haru for the past 20 years, but Aoyama Haru doesn’t seem to realize her feelings for him. She talks about this situation with her childhood friends Iori and Mio and decides to give up on her feelings for Aoyama Haru. But, it's not easy for Kagaya Kaede to disconnect her feelings for him. Meanwhile, Iori has liked Kagaya Kaede since he was an elementary school student. He approaches her. Seeing this, Aoyama Haru becomes disturbed. In fact, Aoyama Haru made a promise with Kagaya Kaede’s late mother and he is honoring it. Adapted from the manga series "Otona Najimi" (おとななじみ) by Nakahara Aya (中原アヤ).