People frequently associate yawning and placing one's arms behind one's head with preparing to kick back and relax after a long day at work. The pose is associated with relaxation and is not usually appropriate for public places. This pose, however, is quite common in shonen anime, particularly among male characters who walk around with their arms behind their heads, sometimes yawning and keeping their eyes closed. Shonen anime boys who walk around like this are usually described as laid back, easygoing, and sarcastic.
Of course, these same characters also have the ability to eliminate large numbers of people easily. This pose is typically used by characters who are brilliant but enjoy taking it easy or refusing to put in the effort because they detest giving everything they have. Shikamaru from Naruto and Karma Akabane from Assassination Classroom are both excellent examples of this trope. Killua Zoldyck from Hunter x Hunter is also renowned for striking this pose while accompanying Gon. Even female heroes, like Midnight from My Hero Academia and Shura from Blue Exorcist, are known to strike this pose. One essential characteristic unites all of these characters.
Relaxed Anime Characters Enjoy Lounging Anywhere
The brilliant hero with an abundance of power, but no motivation to do anything with it, is one of anime's most common tropes. For example, Karma from Assassination Classroom is a brilliant strategist with wits that surpass any of his peers, but he landed himself in a class full of delinquents because he's too lazy to apply himself academically. Naruto's Shikamaru is the same way. He often walks around sighing and calling everything that requires even a tiny bit of effort a "drag."
Another common shonen trope is for an overpowered hero to know they have a ton of power at their disposal, but they're so confident that nothing fazes them. They often walk around with a smug grin on their faces and make major accolades seem like everyday errands. Characters like Killua from Hunter x Hunter and Satoru Gojo from Jujutsu Kaisen are the best examples of this.
The majority of these characters have been seen strutting around with their arms behind their heads as if everywhere they go is a suitable lounging spot. The pose is frequently accompanied by a well-placed yawn and a snarky one-liner for every situation in the case of fan-favorite slackers like Akame and Shikamaru. Characters such as Gojo or Killua frequently do it to demonstrate how they go through life carefree and how it's easy for them to relax because they're confident in their abilities.
What Distinguishes Some "Hands Behind the Head" Characters from the Rest?
Many other diverse personalities of anime characters have posed and moved around with their arms behind their heads. Some simply seem more appropriate for this trope than others, though. Some characters engage in it while they are thinking. Others are tsundere anime boys who do it to appear unconcerned with their surroundings, despite the fact that they are carefully listening to a conversation.
However, those who feel the most "at home" with this relaxed pose are the ones who are genuinely carefree and don't care what others think about them. Though the average person wouldn't walk around like this in real life, it makes sense to see it in anime since it helps flesh out certain characters while establishing their roles in the story. Many characters who pose like this are lazy slackers who don't apply themselves, but others are immensely powerful legends who can always rest assured in their own abilities.