Volume 5 contains the side story "Kimi to Watashi to 5-gatsu no Niwa" (きみと私と5月の庭, You and Me and the May Garden).
Volume 6 contains the side story "Lovers Name" (LOVERS NAME).
Volume 14 contains the side story "Himitsu" (秘密, Special Episode: The Secret), chapters 77~79.
Natsu no Ori (夏の檻, The Cage of Summer); Hana to Yume 1996 #18
A young girl's male cousin comes to visit her and her family. Over the course of the summer he blackmails her. One day everyone in the house leaves for different reasons and something...different...happens.... Some would call it gross and some would call it love.
Kawaki no Tsuki (渇きの月, The Thirsty Moon); Hana to Yume 1997 #2
Miho is saved from some perverts by Yue. When she meets him again, she develops a crush. However, her fiancee recognizes Yue as someone from the past... and it's not good news. (Source: MU)
This is about Umeda's school years, and how Umeda and Kijima met.