Here is the full list of all 15 Kinkoi: Golden Time achievements.
Finish Maria's Route
Get all Achievements
Start Maria's Route
Finish Ayaka's Route
Start Ayaka's Route
Finish Append Reina
Finish Append Sylvie
Finish Append Elle
Finish Append Ria
Finish Append Akane
Finish Append Mina
Finish Mina's Route
Start Mina's Route
Complete the prologue
Start the game