If you're looking for manga similar to ef - a tale of melodies: Prologue, you might like these titles.
Tetsuya Mizuno, a third year high school student, meets Yuzuko Sanada, a childhood friend whom he nicknamed Yuzu one day on his way to school. Yuzuko actually has a crush on Tetsuya. To her advantage, she is skilled at cooking and homemaking, but has a timid personality. He later also meets Rui Nakane at the pool after running errands for Asumi Akiyam, his cousin who is also the school nurse. Rui holds vast knowledge, and is very affectionate towards animals to the extent where her aim is to become a veterinarian. Despite her love toward animals, she has a severe fear of touching cats due to a past incident...
Kaede loses her memory so Rin and friends must help her recover them! Phoenix Wright style! Rin and Kaede's childhood friend, Sakura returns and a new love triangle begins.