What a strange little piece of internet folklore the 'Shinji chair' image has become — I love how tiny fan sketches explode into global memes. From what I can tell, there isn't a single, universally agreed-upon credited creator for the original artwork. The image feels like classic fanwork: a simple, expressive drawing of Shinji from 'Neon Genesis Evangelion' sitting awkwardly on a chair, and it began circulating widely across imageboards, Twitter, Pixiv, and Tumblr. Different communities picked it up, remixed it, and attributed it to various users, but the earliest clear provenance seems murky.
I spent time following repost timestamps and cached pages, and the pattern is typical: one or two Pixiv or Twitter posts pop up, then dozens of mirrors and edits. At several points the trail hits deleted accounts or anonymous imageboard posts, which is why people argue about the “original.” There are claims that an anonymous Japanese user uploaded an initial sketch on an imageboard and someone later reposted it on Twitter, but no definitive signature that survives.
Ultimately I treat this as a fan-created meme that belongs to the community more than to a clear single author — that can be frustrating if you're trying to give credit, but it's also kind of beautiful how a tiny drawing of a sulky character from 'Neon Genesis Evangelion' traveled so far. I still get a chuckle picturing Shinji getting dragged into meme culture, honestly it makes the character feel oddly at home online.