Asuma Sarutobi

was the leader of Team 10, consisting of Shikamaru Nara, Choji Akimichi and Ino Yamanaka.

Background
Asuma was born the son of the Third Hokage, and in later years would become the uncle of Konohamaru. He at some point in time had a disagreement with his father and left Konoha to pursue his personal interests. During his absence he became one of the Twelve Guardian Ninja, a group who protected the Land of Fire's daimyo, indicated by the sash on his waist. Prior to returning to Konoha to resume active military duty, he accumulated a bounty of 35 million ryō, something he seemed to be particularly proud of.

Personality
Asuma was typically a laid-back individual, and did not get himself involved in things unless necessary, as seen when he decided not to help save Hinata Hyuga during the Chunin Exams. He was often seen smoking a cigarette, and smoked about two packs of cigarettes a day. Despite this, he would break the habit when something was bothering him, such as when the Third Hokage died. He would also stop smoking if "something is going on", as seen prior to his last encounter with Akatsuki.

Asuma had a very close relationship with his team, even though he believed it to consist of a "glutton" (Choji), a "loud mouth" (Ino), and a "slacker" (Shikamaru). To help them overcome their underachieving natures, he attempted to use bribery and outright trickery to manipulate them into doing what he wanted. This was seen most with Choji, who Asuma was frequently able to entice into action with the promise of food.

It had been heavily hinted that Asuma was romantically involved with fellow Jonin Kurenai Yuhi. The two appeared together in most of their scenes, and the other characters made it a point to note this fact on several occasions. When Kakashi Hatake found the two together at a dumpling shop, Kakashi asked if they were on a date, to which Asuma responded by quickly changing the subject. In a flashback, Asuma was shown buying flowers for a person he refused to name, though Ino asked that he say hello to Kurenai for her anyway. During Asuma's battle with Akatsuki, Kurenai was often shown wondering about his progress, appearing anxious. When she learned of his death, she fell to her knees in remorse, and later laid flowers on his grave during his funeral. The truth of their relationship was made clear in Part II when Kurenai revealed that she is pregnant with Asuma's child.

Of his students, Asuma spends the most time and is closest to Shikamaru. Asuma and Shikamaru play Shogi or Go in their free time, though Asuma was never able to beat Shikamaru. It was Asuma who first discovered that the lazy Shikamaru was actually a genius with an over 200 I.Q.

Chunin Exam arc
When Choji, fearing the competition, contemplated forfeiting his match during the preliminaries of the Chunin Exam, Asuma convinced him not to by offering to take him out for "all you can eat" barbecue (yakiniku or Korean galbi). Asuma also claimed that he'd stop the match if it got out of hand, as the other Jonin did during Hinata Hyuga's match. Both Ino and Shikamaru noted to themselves that Asuma didn't actually help in that instance.

Later, during the invasion of Konoha, Shikamaru was left by himself to defend against a group of imposing Sound ninja. Just as Shikamaru ran out of options and the Sound ninja were about to finish him off, Asuma appeared and single-handedly defeated the group without being hit once.

Return of Itachi arc
During his brief battle with Itachi Uchiha and Kisame Hoshigaki, Asuma managed to catch Kisame off-guard with his trench knives, leaving a slight cut on Kisame's cheek. The rest of the battle went poorly for Asuma, however, and he was nearly hit by Kisame's Water Shark Missile Technique. Kakashi Hatake arrived in time to copy the jutsu and used it to block the attack, thus saving Asuma. Asuma, Kurenai, and Kakashi then faced off with the two Akatsuki members, only for Kakashi to fall victim to Itachi's Tsukuyomi. Might Guy arrived just in time to save him and the other two, and was coaching Asuma and Kurenai on how to fight against a Sharingan-using shinobi when the pair fled to pursue Naruto Uzumaki, their true target.

Sasuke Retrieval and Filler arcs
Prior to Choji's setting out with the squad assembled by Shikamaru to track down the renegade Sasuke Uchiha and the Sound Four, Asuma berated him for eating so much and not training enough. After Choji's recovery from his battle against Sound ninja Jirobo, he quickly regained his lost weight but also approached Asuma for more intense training, which Asuma agreed to with some admiration.

In the anime, Asuma and Kurenai were dispatched by Fifth Hokage Tsunade to bring the criminal Chunin Mizuki in for questioning regarding his suspected involvement with Orochimaru. The pair arrived at the Leaf Village Maximum Security Prison only to be greeted by a swarm of released inmates, including the Legendary Stupid Brothers Fujin and Raijin. Outnumbered, the two were beaten into unconsciousness and quickly rushed to the Leaf Village hospital for medical treatment.

Part II
Asuma made his Part II debut standing at the Third Hokage's grave, where he commented on how he's finally beginning to understand what the Third had taught him. Asuma confessed that he'd always been detached from Konoha, but after seeing how his father sacrificed himself for the village, he was now proud to be a member of the Sarutobi clan.

Later when Naruto begins training to master wind-chakra, he comes to Asuma who is also a wind-type user for help. Asuma agrees to give him pointers if he agrees to pay for his teams next meal (which Naruto forgets includes Choji).

Fire Temple filler arc
After hearing about the attacks on villages that border the Land of Fire, Asuma was teamed up with his students to investigate. To his dismay, each of the said villages were completely wiped out. Upon returning to Konoha to report, he discovered that Sora, the son of his former Twelve Guardian Ninja teammate, Kazuma was temporarily made part of Team Yamato while Sai was recovering.

Initially, Sora was rather indifferent with Asuma despite the fact that he was once an ally of of his father, but after Asuma agreed to teach him along with Naruto how to effectively use wind element chakra, Sora began to warm up to him. Quickly, Asuma realized that Sora had unusually strong chakra not unlike Naruto. As a further act of kindness, Asuma had Sora's broken tri-bladed death claw reforged with the same special material that was used to make his trench knives.

Sora unfortunately later learned the truth about Asuma's relation to his father, learning that it was Asuma who killed him. In a fit of rage, Sora attacked Asuma, using all he learned from Asuma against him. Asuma managed to incapacitate Sora, but Sora's was still too filled with rage to listen to Asuma, causing him to run from the village.

Later during an attack on Konoha, Asuma discovered the true plan was to resurrect the four lightning-chakra users of the Ninja Guardians so they could use the Limelight jutsu to destroy Konoha. After being initially defeated by his former friend, Kitane, he managed to "kill" him and stop the completion of Limelight. He then discovered that the mastermind behind the invasion was none other than Kazuma himself. After a heated battle, Asuma managed to defeat Kazuma. As Kazuma died talking about the future of the Fire Country, Asuma calmly said that its future will be fine, because he would see to it that its true "king" remains safe.

Hidan and Kakuzu arc
Asuma was teamed up with Shikamaru, Kotetsu Hagane, and Izumo Kamizuki as members of the Niju Shotai. His team, along with the entire group, was ordered to search for and, if possible, capture a pair of Akatsuki members who had entered the Land of Fire. Asuma and his team eventually tracked down the Akatsuki members, Hidan and Kakuzu, at a Bounty Station where they quickly discovered that Hidan was immortal after their first attack. The situation worsened, when Hidan's counter-attack resulted in him becoming 'linked' to Asuma through a curse ritual. Hidan assumed a Grim Reaper-like form, causing any bodily damage to Hidan to be shared with Asuma while at the same time not hindering Hidan at all. Some quick thinking by Shikamaru managed to break Hidan's ritual, allowing Asuma to decapitate him with his chakra-extended trench knives. Surprisingly, Hidan's severed head started to talk, uttering expletives at Asuma and Kakuzu (for not helping him).

Kakuzu finally stepped in as he admonishes his partner for letting his guard down and sewed Hidan's head back onto his body. With his body restored, Hidan resumed the ritual and impales himself in the heart. Though the blow did not instantly kill Asuma, it was still quite fatal. The rest of Team 10 arrives as backup, which, combined with a telepathic call from Pain, forced the Akatsuki duo to leave. Before dying, Asuma left some parting words with his students, and smoked one last cigarette.

Later, while Shikamaru was exacting revenge upon Hidan for killing Asuma, Asuma appeared before Shikamaru and congratulated him for finally defeating the immortal. After entrusting his "will of fire" to Shikamaru, Asuma disappeared in a puff of cigarette smoke just before his student finished off Hidan with a huge explosion. Also on his memory from the flashback, Shikamaru was finally able to understand who the king of shogi was in the real world. It is the next generation of shinobi, like Asuma's and Kurenai's unborn child, and how they would learn to care and live peacefully by the great shinobi in the present day. That was why Asuma entrusted his baby to Shikamaru as apprentice and future sensei.

Abilities
Asuma's battle style revolved mainly around taijutsu combined with his trench knives. These knives were made of a special metal that was capable of being infused with chakra. With his Flying Swallow, he could extend the blades with his chakra to injure an enemy several feet out of the physical blade's range.

When demonstrating his wind-based chakra for Naruto Uzumaki, Asuma explained that these chakra-covered blades (when utilized by someone with wind-based chakra) possessed enough power to pierce through rock. During the invasion of Konoha, Asuma was able to use these blades in unison with his taijutsu abilities to single-handedly defeated nine Sound ninja (considering that Pakkun earlier stated they were Jonin-level, it was quite an impressive feat) without being hit once.

In addition to his blades, Asuma could use Fire Release: Ash Pile Burning to breathe out a cloud of superheated ash capable of causing third-degree burns. Because it was ash and not flame, the attack remained in the air around the target, and therefore remained potent for a longer period of time.

Trivia

 * Despite Asuma's tension between him and his father, Hiruzen, they have been shown to have many similarities. They are both regularly seen smoking and have the same style beard and haircut (at least before Hiruzen went bald).

Source

 * First Databook, page 72
 * Second Databook, page 89
 * Third Databook, pages 84-86