Here is the full list of all 15 Kaichu - The Kaiju Dating Sim achievements worth 1,000 gamerscore.
Successfully Date Tephra
Your first encounter with Mechachu
Your first great date
Get the OK ending
Visit every location
Get the bad ending
Successfully Date Mossra
Successfully Date Garudan
Visit 12 locations
Successfully Date Turpio
Successfully date all kaiju
Successfully Date Seadora
Successfully Date Megaricus
Beat the game with only great dates
Successfully date 3 kaiju