Reira Akaba/Relationship

Reiji Akaba
While Reiji and Reira aren't as close compared to other pairs of brothers in the previous series, they still are shown to care about each other. Although they aren't related biologically, Reira was encouraged by Reiji's compliments after his victories during the Maiami Championship and was allowed to join the Lancers despite not being at the Battle Royale. When some of the Lancers complained about Reira joining, Reiji quickly defended him and said that he would not be a hinderance, and constantly shows his confidence in Reira's skills.

When the Lancers were split in the Synchro Dimension, Reira cared about nothing but finding Reiji as soon as possible, and Reiji requested Tsukikage to find Reira and later to take his place in the Friendship Cup. When Reira showed signs of developing a "sense of self", he was shown to be proud and seemingly resents his mother's plan of using Reira as a mindless puppet.

Yūya Sakaki
When Lancers arrived at the Synchro Dimension and were split Yūya immediately noticed Reira's concern over Reiji's whereabouts and his shyness. Yūya quickly became protective of Reira and made it his goal to make the young boy smile. When Yūya was arrested by security he was more worried about Reira's safety and was shown to be relieved when Reira was confirmed to be fine. Yūya angrily scolded Reiji for forcing Reira to participate in the tournament and demanded to know why he made Reira a Lancer, worried that Reira is too young to face the dangers that being a Lancer comes with.

Reira was initially distant towards Yūya and his friends despite Yūya's best efforts to make him open up. And although he didn't show it clearly, Reira grew to have an attachment towards Yūya and feels secure when he is with him. When Reira was scheduled to duel Shinji at the Friendship Cup and became afraid, he immediately ran off to Yūya and hugged him for comfort. He then expressed his desire to become a great Duelist not only like his brother but also like Yūya and also stated his wish for Yūya to win against Jack, showing that Reira has immense trust in Yūya.

After running from Security and dealing with the Obelisk Force, Reira was greatly weakened and recalling his mental trauma; he was no longer in the position to wait for Tsukikage or protect Serena. He was hugely relieved that Yūya came to his rescue at the last minute (ironically thanks to the flare signal) just as another batch of Obelisk Force approaches during the start of the invasion.

Tsukikage
Tsukikage became a protector of sorts for Reira in the Synchro Dimension, rescuing him from Security. However, when Tsukikage replaced Reira in the Friendship Cup, Reira became jealous, desiring Tsukikage's loss. He later expressed remorse over this and apologized, expressing the desire to prove his strength to Tsukikage in addition to Yūya and Reiji.