The artist's fascination with mangas started when he found out about its enthusiastic fans. Up until that point, he had liked and enjoyed them, but when his friend (a big Sega fan) introduced him to the community, Isayama has instantly fallen in love and from that there was no turning back.
Hajime once said that if an apocalyptic scenario would come to reality and humans would get almost entirely wiped out off the face of the Earth by something like a world war, he can imagine himself living (and enjoying) the life of a recluse, on the condition that nobody would disturb him.
He is a big fan of Godzilla and enjoyed the 2016 version of the movie adaptation. He especially liked it for its visual effects and camerawork. Another franchise he enjoys is Neon Genesis Evangelion, this one featuring giant robots. He enjoys Kamen Rider, a famous tokusatsu similar to Super Sentai and Power Rangers. Outside manga, Hajime likes zombies in popular culture and paranormal activity topics. Other inspirations for Attack on Titan include: Gyaos in Gamera: Guardian of the Universe (eating people) Hell Teacher Nube (drawings), Nihei's Knights of Sidonia and works of Kentaro Miura, Toru Mitsumine, Tsutomu Nihei and Hideki Arai.
As for mangas, he prefers the ones with mature and serious themes rather than those written for teenagers, or all age groups. His one clear favorite is ARMS, also known as Project ARMS (MyAnimeList).
Spends a lot of time on the internet looking for all kinds of stuff.
His favorite Attack on Titan character is Captain Levi Ackerman, the enigmatic dark killing machine that Eren works with. However, in one interview he said that his favorite is actually Jean and he mostly likes him for the fact that he is straightforward and says what he thinks.
His favorite scene in the manga is the TV studio takeover.
The fantastic 2009 movie adaptation of the graphic novel Watchmen served as an inspiration for creating the Levi character. Isayama fell in love with Rorschach and melded it with another inspiration - Hiei from Yu Yu Hakusho (Wikia).
For the creation of Beast Titan Zeke, Alistair Overeem served as an inspiration. The Pride, K1 and now UFC fighter has grown pretty big as his career went on and it was all muscle. Isayama is a big MMA fan and he saw plenty of Overeem's fights. Always appreciating the big and scary, he decided to translate some of the Dutchman's qualities into his product.
Another MMA fighter Yushin Okami served as the blueprint for the transformed Eren physique.
Isayama draws both by hand and digitally.
Another of the manga's monstrosities, Colossal Titan Bertolt Hoover was created with the help of an interesting app called 30 Second Drawing App, built on the concept described in the fantastic book Drawing on the Right Side of the Brain (Amazon). The program is available online here, but keep in mind that it's in Japanese only.
Mikasa was the first character the author came up with while developing Attack on Titan. He loosely based her personality on Casca from the cult classic Berserk while not even being aware of it after it was too late. Physically, she was modelled after one woman who came to the internet cafe he was working at after moving to Tokyo. Shortly after he saw her coming in, he started sketching and that's how Mikasa was born.
Those familiar with the military history of Japan probably noticed that 'Mikasa' is also the name of a famous battleship (Wiki). This is not coincidental - Isayama believes that anime characters named after battleships have a tendency to become famous.
Even though he doesn't play the uber-popular free-to-play game Kantai Collection, Isayama feels that had he started, he'd get hooked instantly.
While internet is full of people addressing celebrities in comment sections, forum posts etc., as if they would ever be able to read it, Hajime actually reads a lot of those! He appreciates the fact that people say what they think on the internet and treats all comments concerning Attack on Titan as potential clues worth considering.
For a short while, limited edition of Attack on Titan plum wine was sold. It was made from plums from Oyama (where he was born), and as a symbolic gesture, some that were growing in his backyard were added to the mix as well, so his biggest fans ready up their wallets even faster. On top of that, Attack on Titan juice was also released at the same time. Given the worldwide popularity of AoT manga and anime, that's not much marketing to take advantage of it.
Isayama was the subject of an astonishing amount of death threats. Many seem to be written by foreigners and one reason for it might be the Dot Pixis character from Attack on Titan. His look was based on one of the most accomplished Japanese generals of modern times Akiyama Yoshifuru (Wiki). Hajime admitted it on his personal blog in 2010. Being that Yoshifuru was stationed in Korea during the Japanese occupation between 1910 and 1945, immortalizing him in any form and presenting Pixis as a charming, wise and well-mannered man must be like pouring salt in the eyes of Koreans, even if it wasn't meant as a tribute to the general.
Isayama loves MMA and combat sports in general, but does not hurry to train himself. From time to time, he runs and abuses his chin-up bar.
He doesn't write too many notes when brainstorming and has thousand ideas about everything, which forces him to often check which ones he made use of to make sure that the new ones don't contradict the old ones.
Before Attack on Titan, Isayama was by no means a wealthy man, so when money started pouring into his account, his bank became interested and asked him to come to see if that if it's legal.
Admits to having a "body hair fetish".
Isayama doesn't like food at all! He eats without taking any pleasure from it and has to eat a certain amount not to drop too much weight. On his worst, he gets as low as 40 kg (88 pounds).
