There are 4 volumes total, plus 2 extra editions: extra edition Ayase side & extra edition Mori side (Ch1 - 7 is V1: The beginning & ch8 - 18 is V2: Ayase's route & ch19 - 28 is V3: Mori's route & ch.29 - 38 is V4: The conclusion) Dropped :(
Kare wa Kanojo ni Kawaru no de