Here is the full list of all 54 Record of Agarest War Mariage Mariage achievements.
Married Saika.
Defeated Archdemon Eclipse (Possession).
Reached the ending.
Defeated Valla Fare of End.
Confessed your love to Saika.
Confessed your love to Piadina.
Unlocked Geolette's Plumage power.
Unlocked Saika's Plumage power.
Unlocked Piadina's Plumage power.
Performed unification with Titania.
Defeated the boss of Fool's Tower.
Defeated the boss of Geluire Woodland.
Defeated the boss of Frost Mountains.
Defeated the boss of Star Point.
Titania joined your party.
Defeated the boss of Verde Cave.
Defeated the boss of Gedecht Plateau.
Performed unification with Piadina for the first time.
Performed unification with Geolette for the first time.
Performed unification with Saika for the first time.
Defeated the boss of Creyu Forest.
Defeated the boss of L'Arc Altar.
Married Kunka.
Defeated the boss of Throne of Ire.
Confessed your love to Kunka.
Defeated the boss of Fell Sanctum.
Unlocked Kunka's Plumage power.
Defeated the boss of Rauea Mountain.
Defeated the boss of Zula Desert.
Defeated the boss of Meren Marsh.
Performed unification with Felicia for the first time.
Performed unification with Panina for the first time.
Doze joined your party.
Defeated the boss of Raster Valley.
Cupra joined your party.
Defeated the boss of Hell Maw.
Defeated the boss of Dozy Forest.
Performed unification with Kunka for the first time.
Defeated your first opponent.
Defeated Transformed Lifre.
Defeated Archdemon Eclipse (Soul).
Defeated the EX boss of L'arc Peak.
Confessed your love to Felicia.
Confessed your love to Panina.
Married Felicia.
Married Panina.
Unlocked Felicia's Plumage power.
Unlocked Panina's Plumage power.
Confessed your love to Geolette.
Reached the true ending.
Married Geolette.
Married Piadina.
Married every potential love interest.
Married every potential love interest?