The Shigure Souen Style

Yamamoto's primary weapon is a sword. When Yamamoto first met Tsuna however he had no idea how to use any weapon, much less a sword. Reborn changed that by giving Yamamoto a special practice "bat". This bat, when swung at over 300 km/h, roughly 187mph or 83.33m/sec transforms into a sword, which frankly sounds ridiculous, but apparently works. Yamamoto is able to get by using this transforming blade without training until the Varia Arc. At that point, Yamamoto faces Squalo who beats him and tells him "you have no sword skills". This criticism became a challenge for Yamamoto who put his full strength into finding a way to master the sword.

Yamamoto went to his father who was known for his skill with the sword, despite having retired years ago. His father in turn taught him the Shigure Souen Style. This sword technique that is passed down from master to student by tutorial. The student watches his master perform each technique only once and from there is expected to replicate the technique. Each new master creates one new technique which is added to the style. Therefore, when a teacher has multiple students there become different variations of the technique. Along with the Shigure Souen Style, Yamamoto inherits his father's sword Shigure Kintoki which normally looks like a kendo stick. It turns into a katana when wielded using the Shigure Souen Style.

Yamamoto is unique in that he has added more than one technique to the Shigure Souen Style. All of the later techniques are different from the techniques Yamamoto learned from his father and the first technique he created as a master. The additional techniques don't have "ame" or "rain" in the name and a large amount don't even have Japanese names. It is unclear as to whether they would be taught to a student as an official part of the style or if they are solely for Yamamoto's use. This is because they are techniques developed by Yamamoto as a way of fighting enemies of the Vongola and may even incorporate his short swords. So far we have seen thirteen different unique techniques used by Yamamoto as part of his own sword style; eight Shigure Souen Techniques his father taught him, the ninth technique in the style which he added upon becoming a master and four supplemental techniques created by Yamamoto during his battles as the rain guardian. Additionally, Yamamoto has enough skill to have mastered several of Squalo's techniques.

Yamamoto's Sword Techniques

Shajiku no Ame (車軸の雨 Axle of Rain) - The first technique is offensive, the user charges forwards and and attacks with a straight forward thrust.
Sakamaku Ame (逆巻く雨 Rolling Rain) - The second technique is defensive. The user creates a distraction by stiring up the terrain (usually water) around them. The user then ducks behind the terrain and throws their sword in front of their body in defense.
Yazaru no Ame (遣らずの雨 Last Minute Rain) - The third technique is offensive. The user drops the sword to their foot and sends it flying in a forward stab.
Gofuu Juu (五風十雨 May Wind, October Rain) - The fourth technique is defensive. The user hides themselves from attacks by synchronizing their breathing with that of their opponent.
Samidare (五月雨 Early Summer Rain) - The fifth technique is offensive. The user slashes diagonally, dropping the sword into his other hand as he continues they attack.
Unknown sixth technique. Based on the order of the techniques by type most fans have guessed that this technique is defensive.
Shibuki Ame (繁吹き雨 Splashing Rain) - The seventh technique is defensive. The user holds the sword backwards and then spins in in order to create a whirlwind that acts as a shield.
Shinotsuku Ame (篠突く雨 Pelting Rain) - The eighth technique is offensive. The user uses the blade of the sword to cut all around the water and their opponent trapping them and throwing them off balance before delivering a single concentrated strike directly to their body.
Utsushi Ame (うつし雨 Duplicate Rain) - The ninth technique is offensive. The user makes a tidal wave in the water and while the opponent is distracted by the reflection of the water the user attacks from above.
Scontro di Rondine (燕特攻 Clash of the Swallow) - An offensive technique used in the future Yamamoto. A tidal wave of rain flames surround him while he charges led by the swallow from his box weapon. This is similar to Squalo's Scronto di Squalo.
Beccata di Rondine (嘴の燕 Swallow's Beak) - An offensive technique introduced in the future arc where Yamamoto thrusts his blade multiple times using just one of his hands. This is similar to Squalo's Zanna di Squalo.
Aggregate Art: Jiunoka (時雨之化 Rainy Metamorphosis) - This form in unique in that it is considered to be both defensive and offensive. First used in the future arc. Yamamoto combines his techniques to strike moving objects with his rain flames causing them to appear frozen.
Sadachi: Kirisame (Left Blade: Drizzle) - This technique is offensive. It is introduced during the Shimon arc when Yamamoto first uses his Cambio Forma Version Vongola Gear to "sniff" out his enemy using his old box weapon Jirou and attack using compressed airwaves to cut the enemy into pieces.
Udachi: Kirisame (Right Blade: Drizzle) - This technique is offensive. It acts as the twin technique to Sadachi: Kirisame and was introduced during the Shimon arc as well. It acts just like Sadachi: Kirisame with one difference. Instead of using Jirou, he uses Kojirou to track the enemies that Jirou has caught the scent of.
Attaco Di Squalo - This technique is one Yamamoto Takeshi uses in the future. It is one he learned from Squalo. The technique releases an oscillating wave that paralyzes the opponent's muscles. Yamamoto makes this more effective by adding rain flames.