Yu-Gi-Oh!, Season 3: Enter the Shadow Realm

Tristan:
We can't let Joey go through with this duel! This is exactly what happened when Marik dueled Mai! It's too dangerous!

Duke:
Let's step in!

Tea:
Joey's already made up his mind. Didn't I tell you what he said to me?

Yami-Yugi:
What's that?

Tea:
Sorry, Yugi. I should have told you about this before. [Flashback to her and Joey's conversation] Joey and I had a conversation after Mai's duel with Marik.

Joey:
I know if I beat that evil freak in a duel, I can get Mai back!

Tea:
Are you sure about this, Joey?

Joey:
I've never been more sure of anything in my life. I owe it to Mai and to myself to face Marik. If I back away from this fight now, I'll never be able to forgive myself. I've made up my mind. I gave Mai my word that I wouldn't let anything happen to her, and Joey Wheeler would never break a promise to a friend… So look out, Marik, 'cause here I come!

[Flashback ends]

Tea:
So Joey's trying to rescue Mai out there, and nothing we say can stop him!

Yami-Yugi:
I thought so!

Yugi:
There's gotta be something we can do to save Joey! I know he promised to bring back Mai, but there has to be another way!

Yami-Yugi:
Yugi… It's his fight. Just as Joey made a promise to Mai, we made a promise to Joey that we would stop protecting him. We must prove to Joey that we believe in him by letting him duel on his own.

Yugi:
We can't!

Yami-Yugi:
Trust him, Yugi! He can win, but he needs our faith and support.