ughhhhhhhhhhhhh this is going to seem cliche but hold out with me here
He's most grateful for Yugi.
Like I know I rant about this shit a lot, about how he loves Yugi and such. And don't get me wrong, he adores Yugi, but there's more to it than just the fact that he adores Yugi. He's grateful to Yugi, because he would literally be nothing without him.
Yugi solves the puzzle; freeing him from his prison of darkness. Upon gracing the waking world once more, he responds by going, put it nicely: Batshit Bonkers™. However, Yugi, though somewhat afraid by this, does not try to destroy him or anything of the sort, but tries to help him. He helps Yami stop being so crazy, think a little more clearly, become more of a "partner." He's making a choice by letting Yami take over by Duelist Kingdom, he wants to let Yami help.
By Battle City, Yugi literally puts his life on the line to save him. He nearly burned to death in order to save him and the puzzle. Yugi shares his body and wants to be with him forever.
Waking the Dragons, Yugi sacrifices himself so the Pharaoh's soul isn't lost.
Millennium World, he leads the cause in finding him, in finding his name, in helping him learn it.
Yugi literally saved his life, several times, while welcoming him to share his body as a partner. He was essentially a parasite to Yugi, living off his body, but Yugi only responded with kindness, compassion, and a desire to help him, and that is what he will forever be most grateful for.
"what are you most grateful for?"
He's most grateful for Yugi.
Like I know I rant about this shit a lot, about how he loves Yugi and such. And don't get me wrong, he adores Yugi, but there's more to it than just the fact that he adores Yugi. He's grateful to Yugi, because he would literally be nothing without him.
Yugi solves the puzzle; freeing him from his prison of darkness. Upon gracing the waking world once more, he responds by going, put it nicely: Batshit Bonkers™. However, Yugi, though somewhat afraid by this, does not try to destroy him or anything of the sort, but tries to help him. He helps Yami stop being so crazy, think a little more clearly, become more of a "partner." He's making a choice by letting Yami take over by Duelist Kingdom, he wants to let Yami help.
By Battle City, Yugi literally puts his life on the line to save him. He nearly burned to death in order to save him and the puzzle. Yugi shares his body and wants to be with him forever.
Waking the Dragons, Yugi sacrifices himself so the Pharaoh's soul isn't lost.
Millennium World, he leads the cause in finding him, in finding his name, in helping him learn it.
Yugi literally saved his life, several times, while welcoming him to share his body as a partner. He was essentially a parasite to Yugi, living off his body, but Yugi only responded with kindness, compassion, and a desire to help him, and that is what he will forever be most grateful for.