Notes:

Translations of parts of article, about story:
Two original protagonists. They are twins from the Kingdom of Aitriss and the children of Queen Yuana.
Shion: Prince of Aitriss. Aspires to be a knight who fights on the front-lines rather than a king and thus encourages his twin sister Lian to inherit the throne.
Lian: Shion’s twin sister. Clever and understanding of her own faults, so she has no desire to inherit the throne. Rather, she encourages Shion to become king.
After Shion and Lian’s father died of illness, the kingdom was left without a ruler, but thanks to the aid of the neighboring kingdom of Guston, order and harmony were maintained. However all this came to an abrupt end after monsters from another dimension invaded.
The story begins right as the kingdom is suddenly attacked. Shion and Lian who have only known peace until now find themselves attacked by monsters and are separated from their mother. While visiting, Prince Darios of Guston helps Shion and Lian escape the castle by request of their mother… From here, a battle to reclaim their homeland begins. But what will happen next?
Darios: Prince of Guston. He taught Shion the way of the sword and Lian the academic arts; and is like a big brother to them.
Yuana: Ruling queen of Aitriss after the king passed away. Though she’s troubled by Shion and Lian both unwilling to inherit the throne, she gently watches over them as they grow up.

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Bits of gameplay info:
Game will be fully voiced and there’s a large amount of dialogue.
Most playable characters are from Shadow Dragon, Awakening, and Fates. They decided against having all the protagonists from each game since most of them primarily wield swords. As such, it would imbalance the game's weapon triangle system.
You can switch characters mid-battle. Players can control characters with various weapons and classes such as archers and mages. There are more characters here compared to other Warriors collaboration titles' first installments (I.E., sequels are not counted).
Speaking of weapon triangle, it works as usual. Swords are strong against axes, etc. There will also be bonus damage such as fliers being weak to bows. Also, mounted characters will generally stay on their mount.
Support conversations are included. Many conversations, ranging from serious to silly, are in. Conversations are all purely platonic. No romance or marriage.
Game is still slated for Fall 2017 release (in Japan). Game is about 70% done.