The story follows a group of middle school students who are suddenly transported to an alternative dimension where some of them gain supernatural powers.

While fantasy elements are present, the series primarily uses its setting to explore psychological themes such as identity, social expectation, freedom, and loneliness.

[3] Producer Motoki Mukaichi had met with Natsume previously while working on Space Dandy, and he decided to offer Natsume the opportunity to produce an original series about anything he liked, making only minimal suggestions, such as the constant use of cliffhangers, thus giving him a great deal of creative freedom for the creation of Sonny Boy and the possibility to choose people for his team.

The art director Mari Fujino decided to have traditionally painted backgrounds and settings, taking inspiration from painters like Henri Rousseau, and making constant use of complementary colors that, in her view, matched Natsume's writing.

[6] Ging Nang Boyz [ja] performed the series' theme song "Boy Meets Girl" (少年少女, Shōnen Shōjo, lit.

'Boy Girl'),[3] with Sunset Rollercoaster, VIDEOTAPEMUSIC, The Natsuyasumi Band, Ogawa & Tokoro, Mid-Air Thief, Kaneyorimasaru, toe and Conisch providing additional original songs created exclusively for the anime.

[2][4][1][15] Director Shingo Natsume declared in an interview that one of his main objectives was to show the friction between maintaining order and individual freedom, saying "[t]he story is inspired by the illogicalities that can sprout through rules".

[4] Collider's David Lynn comments how the show "addresses themes of capitalist exploitation, social isolation, and the power of community", constantly presenting many different philosophical topics, and "not so much answering any questions as much as asking and then pondering on them"[15] In his honors thesis, Inoue (2023) analyzes two anime with multiverse settings, The Tatami Galaxy and Sonny Boy, comparing them and commenting how they explore the experiences of Japanese adolescents growing up in their country's modern society.

[16]: 11–13  He also comments on the growth of protagonist Nagara throughout the series, deeming it the main message of the show: he starts as an apathetic individual with a very nihilistic outlook of life, but changes to a more optimistic attitude later on due to his interactions with Nozomi, who has a more positive disposition from the start, which is reflected symbolically in her superpower, a “compass” that allows her to “see the way out” of the darkness surrounding the school in order to return home.

[22][23] Sonny Boy has received favorable reviews, having been called one of the best anime of its season[28][29] and of its year,[15][30][31] and it has been noted as particularly original within the isekai genre.

[5] Collider's David Lynn comments that although some initial parallels to Lord of the Flies can be drawn, the series "expands far beyond simple comparisons to its inspirations" addressing many different social and philosophical topics, and "ultimately challenging its characters to consider the very purpose of life".

Lynn also notes that while the non-traditional narrative might be a major turn off for some, the series still offers compelling stories without falling into "despondent nihilism".