Yuya-Yuto: Fast friends. They talk about everything together, but sometimes have disagreements!
Yuya-Yugo: Instant friends. They bicker sometimes (mostly because Yugo can't keep his mouth shut), but overall, they get along really well!
Yuya-Yuri: Difficult at first. Yuri causes problems, Yuya tries to mediate, but he also believes in Yuri. Once they sort everything out, they're very close.
Yuto-Yugo: Volatile early on, but they quickly work things out and become friends. Yuto sometimes berates Yugo for his stupidity, but other than that, they get along great!
Yuto-Yuri: Difficult at first because of Yuri's troublemaking nature. They work things out eventually, and bond in a way the other boys can't - intellectually!
Yugo-Yuri: These two take the longest to reconcile, just because Yuri likes to bully Yugo. It does happen eventually, and they bond over the surprising number of similarities they share!