Here is the full list of all 15 Kinkoi: Golden Loveriche achievements.
Finish Sylvia's Route
Start Sylvia's Route
Finish Common Route
Start a new game
Start Reina's Route
Finish Reina's Route
Start Elle's Route
Finish Elle's Route
Start Ria's Route
Finish Ria's Route
Start Akane's Route
Finish Akane's Route
Reach the True End
Unlock the Hidden Special End
Unlock all Achievements