桜 says:
yep.
anyway.
Aqua was told by Master Eraqus that if anything happened to their home, to take his keyblade and seal it using a special seal that he knows.
Eraqus was killed by Terra because he was attacking Ven.
Ven had to mix with Vanitas to create the x-blade, which is what Vanitas is wielding in the picture I showed you.
At the end they finally did it, which is what made his heart sleep.
So she did so.
And their home became Castle Oblivion.
A maze where only Aqua would know her way through.
Aqua leaves Roxas there.
I mean.
Ventus.
And he sleeps dormant.
But Riku told Sora (at the age of like 6).
After Sora said he felt someone needed his help.
To open his heart and ask that person what they needed.
And he did so.
And Ventus answered, forming a strong connection between them.
Ven and Sora were now connected by heart.
The rest here is my guesses from the storyline.
This gave Sora the ability to use the keyblade, though.
Ven lie there dormant for ten to twelve years.
In Kingdom Hearts 1, Sora is turned into a heartless.
However, he was able to come back without gaining his heart back.
The reason for this is because it was Ventus's heart that was released.
And the "nobody" that resulted was Roxas: ventus reborn, birth by sleep.
Thus Roxas was released at the end of Kingdom Hearts I.
He immediately starts with no memories in 358/2 Days.
He has no memory of his past whatsoever.
Meanwhile.
Sora moves on to Castle Oblivion in Chain of Memories.
There, the organization manipulates his memories.
As he gets through, Namine changes memory after memory, thus resulting in Xion.
Sorta.
At the end, Namine tries to change them back.
But some memories get away.
So she tells him to sleep in the capsule until she can "fix" him.
But he can't be fixed until Xion is returned to him.
Thus the ending of 358/2 Days.
A CONNECTION TO EVERY OTHER KINGDOM HEARTS GAME
OMG