A Common Boys Name.

The Vongola Familiga is known to be one of... if not the most powerful mafia family in Italy. Their heir, our protagonist, Sawada Tsunayoshi caused the Vongola IX to send a 'tutor' to Japan to train him to take over the family. The tutor Reborn feels that one important piece of training for Tsuna is to help him build up a strong family who can protect him. For the first part of the manga we are unaware as to why Reborn feels that Tsuna needs to build up a family so seriously.

As it turns out the Vongola, while being a rather large family has an inner circle that is meant to surround and protect the boss. Thus the Vongola Guardians exist. They all have a specific trait that makes them worthy of standing beside their boss. In Tsuna's case the majority of his guardians are loyal to him and would do anything for him especially the ones who were with him from the start, Yamamoto and Gokudera.

All of the guardians are given a ring, the ring has a very specific symbol on it because each guardian represents a type of weather to surround their boss "The Sky" Yamamoto's ring represents Rain.

"The ring of rain... the shower that washes away everything." Ch.86, Pg. 03.

Yamamoto represents the rain quite literally. He is the one whose smile and light can make the others feel at peace and give them the confidence they need. It when Tsuna and Gokudera see that even after ten years Yamamoto hasn't changed they're comforted that they can fight and survive in a strange world. Yamamoto is the emotional support and one who can lighten the mood and was away the others sadness when they need it.

There's more to the rings than that though, they're also symbols of virtue I suppose. The Varia members who fight the guardians for the right for their boss to be the true heir of the Vongola are all meant to be the seven sins: Lust, Envy, Sloth, Pride, Avarice, Gluttony, and Wrath. Therefore it is only appropriate that Tsuna's guardians represent virtues those of: chastity, Charity, Zeal, Humility, Generosity, Moderation, and Patience. Because Yamamoto's opponent, Squalo is meant to be Pride, the virtue Yamamoto represents is humility.

This quality fits Yamamoto because he is willing to give up everything to protect his family and friends. Takeshi refuses to give up against a much stronger Squalo because his death would make his friends and family sad and would render him unable to protect them. He refuses to make hard or killing blows against Squalo and even attempts to save Squalo after he wins despite the fact that it would endanger his own life. Also in the Ten Years Later Arc Takeshi's appearance shows that even though he plays baseball on the side he has ultimately given up his own dream in order to fulfill his responsibilities to Tsuna as one of his guardians.