Here is the full list of all 20 Kare wa Kanojo achievements.
Complete Rika's route
Get a kiss from Rika
Grope Rika (accidentally)
Help Rika with the festival
Complete Nanami's route
Help Sakura tell the truth to Nanami
Prank your friends with Nanami
Get a kiss from Nanami
Finish the game for the first time
Complete Sakura's route
Complete the fifth chapter
Complete the fourth chapter
Get a kiss from Sakura
Complete the third chapter
Find the truth about Sakura
Complete the second chapter
Tell Sakura the truth about the yukata
Complete the first chapter
Choose to game at the beginning of the game.
Find the secret code in the game