Here's my explanation of why Seto isn't himself:

Darkness.

Darkness was everything I ever saw anymore.

No light.

I've kept to my room because of what in turning into

What I am.

A monster,

A Dark Sorcerer.

Ninja suddenly teleported into my room.

I did what I thought was right,

I immediately teleported to a place no one knew about,

Where no one could find me,

Where no one could see me in this state.

The Library.

I didn't want to hurt anyone.

Now she's gone.

It's all my fault.

It's all my fault.

I'm the one who should be gone, not her.

She should be here.

Smiling and protecting everyone.

Making everything better.

She was a little sister to me.

Even though she was different than most.

The most kind-hearted person I knew.

And she's gone.

Because of him.

--------------------------------------------

Well, that was

Depressing.