Shigeto Yamagara is an original creator known for the multimedia project Everlasting Heart, also known by its Japanese title Kimi to Boku. His work originated in the early 2000s as a self-produced Flash anime short, which he later expanded into a published book and a live-action film adaptation. This project is noted for being one of the earliest examples of an online Flash-based anime, launched in 2001, and it serves as the cornerstone of his public creative identity.

The story of Everlasting Heart is autobiographical, depicting the decade-long friendship between a young man aspiring to be a manga artist and his cat, Ginougou, with the narrative told from the cat's perspective. The live-action film adaptation was released in Japan on May 14, 2011, with a running time of 45 minutes. For this version, Yamagara is officially credited as the original story creator, while the screenplay and direction were handled by Takashi Kubota. The cast included Aoi Nakamura as the young man and voice actress Maaya Sakamoto, who also performed the theme song, as the voice of the cat.

Yamagara's approach to creation is rooted in independence. He has expressed a preference for publishing his work on his own terms before considering commercial restructuring, viewing his success with Everlasting Heart as a potential business model for other young creators. He emphasizes that success requires not only artistic technique but also skills in production and promotion. In a 2011 interview, he stated that his work is a means to communicate messages and referred to it as his lifework.

His artistic influences include seminal figures in manga and anime, such as Osamu Tezuka and Fujio Akatsuka as manga artists, and Osamu Dezaki and Akio Sugino as animators. He has cited manga series like Mugen no Junin, Historie, and the JoJo series as personal favorites. Following the completion of the live-action Everlasting Heart film in 2011, Yamagara announced plans to create a new animated work centered on themes of animal rescue and pet loss.