Shingo Sawatari/Relationship

Mr. Sawatari
Mr. Sawatari is Shingo's father. Shingo has a close relationship with his father and both cares for each other. From Shingo's personality, it's very clear that Mr. Sawatari always pampering and spoiling his son, showing how much he is fond of him. Hearing the attack of his son angered him enough to abuse his position as a high-ranking official in Maiami City to capture and severely punished the one he deemed responsible without further investigation. Shingo is really attached and dependent of his father, often using his father's connection to get what he wants and likes to boast how great his father's connection is. He was offended when hearing his father was attacked and declared one of his three grudges against Yūya is for attacking his father (not knowing that the real culprit was Shun at that time). His affection for his father was also shown when Tokumatsu forced him to jump while escaping from the Arrest Corps and Shingo cried out for his father.

Reiji Akaba
Shingo is shown to greatly admire Reiji's dueling abilities as shown when he bragged about how he was well known for his multiple summoning methods to Dennis. Reiji in return, is shown to have some faith in Shingo's abilities as shown by how he entrusted Shingo with the task of taking Yūya's Pendulum Summons, had him test a Yosenju Pendulum deck, and had him become a Lancer to aide the others during the invasion by the Obelisk Force. Reiji also taught Shingo how to Pendulum summon.

Yūya Sakaki
At first, due to his task of stealing Yūya's pendulum monsters as well as kidnap his friends to force him to duel in order to test them, Yūya immediately disliked Shingo. Shingo's defeat at Yūya's hands and losing the Pendulum cards caused Shingo to form a bitter rivalry with him. However, things changed during their second duel in which they both seemed to care about each other. After generously offering to duel Yūya anytime the latter wanted, they appeared to have buried the past and became friends. Although their behaviors still seem to annoy each other, they still appear to be concern for each other in important scenarios such as when Yūya lost Yuzu and Shingo was defeated and captured by Security. Their common love for entertaining the crowed also helped improve their friendship which also allowed them to work well together in action duels. While he was dueling Yūgo, Yūya who was linked to Yūgo and fighting beside him, was worried about defeating Shingo and sending him underground. This proves Yūya cares about Shingo as a friend.

Serena
Shingo generally gets along well with Serena since their allies. He decided to accompany her when she went looking for Yuzu and the other Lancers and even applauds her skills after her tenth victory. Similar to Chazz's crush on Alexis from GX, Shingo was shown to have a crush on Serena as seen in the ending "Speaking"  and even attempted to kiss her though Serena simply punched him in the face.