Yugi's friendship with Pinkie Pie can be quite adorable at times.
Yugi's friendship with Luna is also adorable and adorkable as well when it comes up
Chapter 5: Yugi is talking to Pinkie (While she's seemingly fast asleep), about how he thinks she's an amazing friend, and how she and her friends fill a hole he has in him when it comes to friendship. He also says that if he doesn't remember his old friends or anything of his old life in the end, that he hopes Pinkie will accept him as a true friend. Pinkie's response, once he goes back to sleep?
Pinkie Pie: *whispering* Of course, silly! We can share all sorts of memories together, because you're already my friend! I promise, Yugi—if you can't remember your old memories, then we can make super-duper new ones, together!
Pinkie Pie's concern for Yugi (and vice versa) during Chapter 7 after they take a bit of a nasty fall that ends up with Yugi injuring his wing.