Rivals to the bitter end The very best way to describe Xanxus' relationship with Sawada Tsunayoshi is bitter rivals. Tsuna is the last candidate that stands in his way from becoming the tenth boss. For this reason, after Xanxus has killed the other three candidates he heads to Japan to kill the last. Tsuna is everything that Xanxus hates about life. Tsuna is optimistic and idealistic. To add insult to injury, Tsuna doesn't even want to be the boss, and is the best candidate for it. Tsuna believes that everyone has good in them, and that his friends will always be there to support him. He is the complete opposite of Xanxus in many regards, not only from the softness of his personality and looks, but in regard to how he treats his men and enemies with compassion. When the two face off in battle, there is nothing but destruction left in their wake. Xanxus' first thought about Tsuna is always that the kid is in his way. He will do anything and everything he can to remove him from power, but he finds himself outmatched. When Tsuna becomes boss of the Vongola, Xanxus supports the Ninth boss of the Vongola rather than ever lending his support to Tsuna. Xanxus' affiliation lies with the lesser of the two evils in his life.

Tsuna deals with Tsuna problems During the TYL arc, Xanxus states that the reason the ten years younger Tsuna is still alive because he allows it. He (believes he) is perfectly capable of killing the child. However, he wants the Vongola at its strongest. In another instance, Xanxus ultimately joins the Representative Battles to fight Tsuna again. He constantly desires to prove himself superior to the Vongola Tenth. That being said, Tsuna realizes that Xanxus is an extremely capable fighter. In the TYL and Representative Battle Arcs, Tsuna relies on Xanxus to assist the Vongola Family. In addition, despite Xanxus' loathing of Tsuna, he realizes that Tsuna keeps the family at its strongest (the base of what he ultimately desires). For that reason, when the Vongola family needs it, Xanxus is willing to help support the family despite Tsuna's leadership. I do genuinely believe that the two are a good balance for each other. On one hand, Xanxus is everything that Tsuna could be so it will keep Tsuna grounded. On the other, Xanxus needs someone to keep him in line, a role which Tsuna fulfills even with as unwilling as he is to be the tenth boss.