Allie is an example of a mother who puts her life in extreme danger for the sake of her son.
Spoilers incoming. Although she ultimately dies from a heart condition, Allie is quick to rescue Oliver from a river before he drowns at the start of the game. For a mother to put her own life on the line and do something like this is the ultimate sacrifice. It's a personification of the love that they have for their children.
Throughout Oliver's adventures, although Allie is not physically with him, she is what keeps him going. He may not see her, but on a transcendental level, she has never left. It is this that makes Ni No Kuni a truly touching story.
This game teaches all of us an important and heartfelt lesson. Even when our mothers might not be with us, the legacy they leave behind always lives on. It sounds cheesy, but it's most definitely true. Through our memories and abundant love for our mothers, they will always remain close.