Luck and Magna

Moments
In their battle with Vetto the two worked together well, having flashbacks of their friendship while thinking about how much the other means to them, and combined their magic to create a more powerful attack. During that same fight Magna declares Luck isn't allowed to leave him behind.

During their fight while Luck was possessed Magna says only Luck would know his next move because only Luck knows how far he's willing to go. He begs, multiple times during the fight, for the elf possessing him to give Luck back, backed up by Vanessa's pleas. Luck's body begins crying while he has Magna in a chokehold, Magna takes that as confirmation that Luck is still inside. Inside of Luck's mind it plays a reel of meaningful things his teammates have said as he regains control of his own body, saving Magna's for last. After that fight Magna embraces Luck when he asks if he's still part of the Black Bulls. When Luck returns to his normal self, kicking Magna in the face as a thank you for freeing him, Vanessa tells Magna it's just Luck hiding his embarrassment and how cute their hug was. Magna tells Asta and Vanessa the hug "Wasn't like that" and Luck tells Magna he should be more honest with himself.

When Henry is rebuilding the base Luck's special request is asking for his and Magna's rooms to be next to each other so Luck can sense Magna's mana and know what he's up to at all times.

Reasons

 * They are paired together in most of the openings
 * They are paired together on most missions
 * They spend most of their time with each other
 * They live together
 * They have created a combination attack with their magic
 * Luck frequently provokes Magna into sparring with him for attention
 * Magna is always fighting to be on the same level as Luck so they can fight side by side