Ironically, he is the kind of person Tsukasa wished to not revive, a greedy man who cares only about his own desires. However, Tsukasa was desperate for a brilliant mind like Senku's to help him. Gen later becomes one of the Five Wise Generals.
As one of the Five Wise Generals, Gen is the most strategic about how to carry out missions (often finding ways to avoid labor if he can); when it comes to enemies, Gen acts as a tactical forecaster, leaving the exact details of planning to Senku (equipment), Ryusui (travel) and Ukyo (recon). Kaseki tends to drag him along to help with crafting if Chrome is busy with Senku.
Gen is a slim young man, close to Senku in height. His hair is split between the right half, which is white with the hair reaching his chin, although the left half is short and black. His eyes are baggy and have a jagged stone mark running down his left eye in an angled line. His petrification scar is healed by his second de-petrification. After Tsukasa's revival, he used paint to recreate his scar.
He wears an overcoat over a yukata and lacks proper footwear.
Asagiri is somewhat full of himself and his abilities, taking pride in his status as a magician and a mentalist/psychologist, along with his knowledge of the human psyche. He is outwardly stoic, staying calm even when at spearpoint when he first arrives at Ishigami Village. However, this facade seems easily broken through, as seen at his shock when Senku addresses him by name. Despite this, he is revealed to be extremely paranoid (though rightfully so), hiding multiple bags of blood in his clothes in the event he is attacked. He has shown signs of perversion, considering sticking by Tsukasa for the purpose of having a harem and hitting on Kohaku. Regardless, Gen is rather quirky and can often be seen speaking in Pig Latin. He tends to be lazy, self absorbed, and perverted. He also shows reluctance in participating in the manual labor involved in Senku's experiments (though given how arduous the labor is, it is understandable). In addition, as stated by Kohaku in his introduction, he is perfectly capable of lying without a hint of stress or change in expression.
While not nearly as intelligent in terms of science compared to Senku, he proves to be his equal and one of his most vital allies due to his ability to understand the human psyche and manipulate people through lies in contrast to Senku's more honest nature. He uses his abilities to promote cooperation and enthusiasm, motivate allies, conduct negotiations, and outsmart enemies. He tends to shift between acting as a ditzy airhead when it suits him (such as to avoid work or going into battle) and an intelligent manipulator. He is confident and is shown to have nerves of steel, even in the face of death.
He is a proud turncoat, openly offering to lie to Tsukasa about Senku's death when he sees his kiln. Gen favors being on the "winning side," although he is also easily swayed by Senku promising him something that appeals to his personal interest. Despite this, he later admits to Senku that he was most likely already won over by Senku's intelligence and ability to move mankind forward. He proves to be loyal to Senku and uses his abilities to help further Senku's plans usually by manipulating people such as promising Minami a special present to get her to relinquish the last bit of the de-petrification potion she had to revive Francois and similarly tricking Ryusui into paying a ridiculous amount of money to board the hot air balloon (though they needed him to board due to his excellent piloting skills).
He shows a surprisingly strong will and level of endurance, being able to survive a death attack from Magma with proper preparation and still go to the Tsukasa Empire gravely injured to report Senku's death. He was also barely able to keep up with Francois walking to the Ishigami village two days straight (a rather difficult feat without food, water, or shoes).
He is capable of genuine kindness, at one point creating a telescope as a surprise birthday present for Senku. He also seems to get along decently well with Suika, a child. He seems to not hold grudges, as he is able to work with Magma and manipulate him without fear, despite Magma having once attempted to murder him.
On a side note, he has frequently stated that his favorite drink is cola and that he cannot handle alcohol.
As a mentalist, he is deeply intelligent and manipulative, having a large knowledge of the human psyche. He is capable of analyzing and understanding obscure messages or drawings with his great knowledge about the human mind; he was able to decipher Kohaku's message by understanding what each image represented from her point of view. Gen is also able to "put [himself] in the mind[s] of [others]", correctly figuring out what they are thinking or planning.
Gen is very crafty, as he anticipated being attacked and created fake blood packs to wear. This saved him from being killed by Magma.
As an expert liar, Gen can fool anyone. When it comes to the post-petrification humans, Gen can easily impress and trick them into believe his tall tales. Though he is equally good at manipulating people from his era (minus Senku, whom he often collaborates with in these cases) with his showmanship. Gen has stated that the best trick of a mentalist is to "make your joker look like the ace of spades".
Gen has three steps to manipulate someone into working for his goals, should the person be strong-willed and therefore hard to trick (like Mozu). 1) Stand by them to build a sense of comradery; standing across from them makes the conversation feel adversarial. 2) Give inaccurate information relevant to the conversation; it will force the target to correct you and give up the correct information. 3) Order them to do the opposite of what you want them to do. Human beings naturally refuse an order by nature, choosing to do the opposite.
Gen is a master of sleight of hand. He also keeps various props hidden within his coat, so he may cause distractions or fake "peace offerings" to buy time.
He also makes for a very convincing female if the need to disguise himself was needed, with Kohaku stating his only flaw was that he was too tall for a convincing woman.
He is capable of mimicking people's voices to the point of being indiscernible from the original.
He seems to be fluent in both Japanese and English. He responded in English when Ukyo was speaking English through the buried phone in order to conceal their conversation from the others present.
- Gen has a low tolerance for alcohol.
- Since the recreation of paper, Gen keeps a deck of crudely made cards with him all the time.
- In addition to the normal 52 cards, he has three jokers.
- Each joker has a phrase on it, but it's unknown if the other cards do as well.
- It's possible Gen knows tarot, hence the phrases.
- Asagiri translates to Morning Mist.
- Gen's name is composed of "gen" (ゲン gene) while his surname Asagiri is composed of "asagiri" (あさぎり morning mist; morning fog), to create Asagiri (Morning Mist).
- Similar to Senku's hair colour, Gen's hair colour has varied throughout the series. It appearing as blonde and blue (Chapter 66 Dr. Stone Character Poll), white and brown (Chapter 25 and 104 colour pages) and blonde and brown (Chapter 95 and 111 colour pages, Shonen Jump Issue 31 2019, and the Viz Shonen Jump Banner of July 2019). In the anime, his hair is white and black.
- Gen ranked 3rd in the 1st and 2nd Character Popularity Polls.
- Gen's hair was black and white before the Petrification Event happened. 
|Male||Taiju Oki • Senku Ishigami • Gen Asagiri • Chrome • Kaseki • Kinro • Ginro • Magma • Ryusui Nanami|
|Female||Yuzuriha Ogawa • Ruri • Kohaku • Suika • Nikki • Minami|
|Male||Byakuya Ishigami • Gen Asagiri • Hyoga • Ryusui Nanami • Senku Ishigami • Shamil Volkov • Taiju Oki • Tsukasa Shishio • Ukyo Saionji • Yakov Nikitin • Yo Uei|
|Female||Connie Lee • Darya Nikitina • Homura Momiji • Lillian Weinberg • Nikki Hanada • Yuzuriha Ogawa • Minami Hokutozai • Mirai Shishio|