Here is the full list of all 15 Kinkoi: Golden Loveriche achievements.
Finish Elle's Route
Start Elle's Route
Finish Common Route
Start a new game
Start Sylvia's Route
Finish Sylvia's Route
Start Reina's Route
Finish Reina'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