Kedamono Damonoけだものだもの; 熱夏野男孩, Kleines Biest (German)

By baka-updates: Your typical romance story between a girl (Konatsu Narumiya) and a guy...except that this guy changes into a pervy girl! He can only change into a girl during the night. Konatsu is the manager of the boys' basketball team, has a crush on the team captain. Unfortunately, the team captain is a complete jerk. When Konatsu confides in another team member, Haruki, about her troubles, their relationship grows closer. The only problem: Haruki is a nice ordinary boy by day, but a pervy girl by night! This manga is on an indefinite hiatus.