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