Shikadai

How Shikadai joined the Tourney
Shikadai Nara is the son of Shikamaru Nara and Temari, and Boruto's best friend, who attends Konoha's ninja academy.[ch. 700] He inherits his father's relaxed unenthusiastic personality and fighting style through the Shadow Imitation Technique while blunt and outspoken like his mother. During the events of Boruto: Naruto the Movie, Shikadai faces Boruto in the Chunin Exam finals and is deemed the winner by default because Boruto was discovered to having cheated during their match.

How to unlock
For both methods, you must fight Shikadai at the Chunin Exams Finals. Alternatively, you can avoid clashing with him by wishing for him from Black Star Shenron, or purchasing him for 640 Smash Coins in the Smash Store. After defeating Shikadai, wishing for him from Black Star Shenron, or purchasing him from the Smash Store, the announcer will say "Someone else has joined the Tourney!" after a Smash Ball appears on the lower-right corner of the screen with a message saying "You can now use Shikamaru's son and heir to the Nara clan, Shikadai!" He will be seen left of Leonard (Fire Force), right of Tsukasa (Dr. Stone), below HUNK and above Nitara.
 * Clear Man the Meat Level 3 with Shikamaru.
 * Play 1692 matches.

When highlighted
Holds his hands behind his head.

After the announcer calls his name
Shikadai extends his shadow as the camera zooms saying "Since when we're you this strong?"

Great Whirlwind Wall (Neutral)
Shikadai creates a minor tornado, which ensnares the opponent, damaging and cutting the opponent, leaving them crashing into the ground after the tornado subsides.

Shadow Claws (Side)
Shikadai sends two claws made of shadows out slicing the opponent.

Wind Style: Vacuum Blade (Up)
Shikadai uses a sword of wind and jumps up slashing three times.

Shadow Drop Jutsu (Down)
Shikadai sends his shadow out to his opponent to make him/her fall through giving some damage.

Shadow Possession Jutsu (Hyper Smash)
Shikadai says "Time to shine!" then extends his shadow out to his opponent. If he hits, he and the opponent dance in unison, then Shikadai throws a bundle of shuriken, trickling the opponent for 9 hits. Shikadai then throws an Explosive Tag blowing the opponent away.

Shadow Stitching Jutsu (Final Smash)
Shikadai punches his opponent in the face, then makes materialised shadows pierce the opponent from below. Shikadai then says "You're giving be a headache." and kicks the opponent's chest, blowing him/her away.

Victory Animations

 * 1) Shikadai rubs the back of his head and drops to his knees with "What a drag."
 * 2) Shikadai does spin kicks then sighs and says "You know, you're impossible."
 * 3) Shikadai extends his shadow then slaps his hands saying "That's a lot of stuff to get ready; Didn't you do any of it?"

On-Screen Appearance
Shikadai runs to his point and extends his shadow, then retracts it saying "I don't care about becoming a Chunin, but if I skip this, my mom will blow a fuse."

Trivia

 * Shikadai's rival is Donald Duck's the red-clothed eccentric cousin, Fethry.