Shun Kurosaki/Relationship

Ruri Kurosaki
The two are siblings, and seeing from Shun's determination to find her, they had a close relationship. He goes as far as to randomly target any Duelist from LDS in attempt to bargain Reiji Akaba for her. His feelings for his sister also makes is strong that he didn't hesitate to threaten Yūto if he feels he's getting in his way.

Yūto
Shun and Yūto appear to know each other for along time. Although there have been disagreements and differences between their ideas, they have a lot of faith and trust in each other. Yūto refers to Shun as his best friend, protesting that the two did not 'run away' from their homeland, while Shun shows concern when Yūto fought with Yūgo when a Synchro Summon was detected and wished to assist his friend if not stopped by Reiji. Shun becomes worried when he couldn't contact Yūto and angrily accused Yūya of harming and stealing Yūto's card.

Reiji Akaba
Despite previously being opposing forces, they team up for their own gains. Shun had hoped to bargain Reiji for Ruri, but ended up joining LDS to find more opportunities to find Ruri. In turn, Reiji has informed Shun on what his father is up to. The two share a common goal, to find Reo Akaba and know what he is up to.

Sora Shiun'in
Sora is shown to be very hostile to Shun. when they dueled for the first time Shun vowed to not to show mercy on the fusion user (not knowing at the time he is a fusion user ) Sora initially treated Shun kindly in their dueled and when he saw sora entertaining him the he began to talk about the days when his in heartland. Realizing that Shun is from Heartland sora decide to show his true colors and taunted him really badly and this then caused him to be defeated and hospitalize. Sora refuse to accept his loss against Shun and develop a deep grudge and hatred for him and when he return to standard Sora successfully got his revenge and defeat Shun brutally.