Shaft’s anime adaptation of the slice-of-life comic strip Hidamari Sketch is marked by the studio’s distinctive and sometimes bewildering animation style, an excellent cast of voice actors and a markedly leisurely pace, even in the context of its genre. It is made particularly unique by its timeline: the events of the first two seasons unfolded in nonlinear order - a handful of episodes from the second season even comprised two stories each, which occurred months apart - and the last episode of the second season occurs the day before the first episode of the first. Both of these scenes jump between points in time in Yuno and Miyako’s first year at Yamabuki High.
The third season modifies this formula slightly - seven half-episodes occur during the year of S1-S2, but all 12 episodes consist either in part or in whole of a linear storyline starting at the beginning of the next year and following the two new additions to the cast. This season introduces something else new, as well: a half-episode taking place three months before the first year.
Now, airing in an anachronic order is in no way unique to Sketch. Suzumiya Haruhi no Yuutsu made a stir the year before with its strange airing order, and in that case matters were exacerbated by the fact that at its core Haruhi had a classically-cohesive plot. Filmmakers both western and eastern have been telling stories in nonlinear order for decades, and nonlinear storytelling has its roots in pre-common-era writing. However, in any case where an artist chooses to tell a story in deliberately non-chronological order, they must have some reason in mind for doing so.
The 2002 French film Irreversible, for example, related its story in reverse to underscore its statements about fate and determinism; the aforementioned Suzumiya Haruhi no Yuutsu, arguably, was aired in the order it was for the utilitarian purpose of mediating pacing issues which become apparent when watching the show in chronological order - all of its disjointed, slice-of-life adventures occurred chronologically after the more interesting main plot had ended. In any case where an author or director chooses to tell a story in a way contrary to the way their audience expects, one must assume there is a purpose or reason to the decision.
It is also worth considering the intent of the slice of life genre - disavowing the classic plot arc for the sake of a more natural narrative, the viewer is in fact simply shown a “slice” of a fictional character’s life, as if it were torn from the middle of their autobiography. The thematic usefulness of this is to communicate a truth about life in a more authentic way by creating not just characters but units of time which the viewer can actually relate to. This is the relevance of Sketch’s strange chronology - it is a core aspect of the show’s thematic commentary on everyday life.
Sketch’s chronology of Yuno’s first year at Yamabuki High is intentionally scattershot and unpredictable; apart from a small handful of interesting coincidences such as the aforementioned first and last episodes of the “first year” arc comprised of the first two seasons, the order of events displays no obvious pattern, and unlike Suzumiya Haruhi which was rearranged chronologically for its DVD release, this random order was preserved in Sketch’s own home release. This is because that very disorder and vehement abandonment of a linear story speak to Sketch’s thematic statement that such elements are completely irrelevant to the things it wants to say.
The characters of Sketch mature over chronological time the way one might expect, but due to the episode order this change occurs in a way which will escape any viewer who doesn’t carefully consider the relationship between chronological and episode order. Yuno is praised for her incomplete sketch about a month after she is inspired to focus on improving her skills - but to the viewer, the events occur in reverse order, with nearly two full seasons between the two events, and her work on the former sketch occurring half a season after it has been put on display. Sketch occurs as a series of vignettes, all but entirely disconnected and related in a manner particularly characteristic of nostalgic reminiscence - important memories and the explanations of those memories and completely unrelated occurrences are related with no semblance of order, and context is filled in unceremoniously as the conversation progresses.
For example, in season 1 episode 3, Yuno is seen caring for a caterpillar in chrysalis. This caterpillar is not actually introduced until the next episode in which she finds him, and hatches two episodes later. In the episodes from season 2 which occur in this time frame, the caterpillar is present again, mentioned in passing as the characters notice it. These offhanded continuity nods serve to forcefully remove the viewer from the occurrence of events, making clear to them that they are witnessing these events from outside, through the lens of the actual characters’ experiences. This stands in stark contrast to most shows of its type, where if there isn’t an explicitly-designated self-insert character for the viewer they are at least treated as an invisible witness to the events as they unfold.
The viewer does not get to grow along with the characters because the characters have already grown by the time the viewer arrives. The denizens of Hidamari Apartments have grown, past tense, into a group of close friends, and the viewer now stands at the edge of this in-group, offered a short tour of its foundation and history. This idea is elucidated best, ironically enough, by the break from this style of storytelling in season 3.
The two most notable differences between seasons 1-2 and season 3 are the introduction of linear storytelling and the two new characters whose stories are told. Nazuna and Nori, new freshmen who just moved in to Hidamari Apartments, arrive in a new environment to find four girls senior to them who have grown into close friends over the past whole year, as summarized by seasons 1-2 - expressed to the viewer in brief accounts of fewer than fifty days out of that year. The linear storytelling in season 3 is much more dense - almost half of the time between the first and last day of the second year covered by season 3 are covered in episodes. Season 3 marks the point where Sketch “begins” chronologically, and the entire past thirty episodes have all been, essentially, flashbacks and backstory for the current season.
In fact, there are a few points in season 3 where this subtext of reminiscence becomes an actual in-story framing device, such as between episode 5A and 5B - Arisawa, a character as-yet unmentioned, calls Yuno by mistake at the end of “future” episode 5A, just before the beginning of 5B which explains when the two first met on a night during year 1. Similarly, episode 2B of season 3 is marked in-canon as Miyako reminiscing about the year before, and episode 3A is told in parallel to 3B to show Yuno and Sae’s comparable sincerity in their respective fields.
The first two seasons of Hidamari Sketch are imbued with a fixation on the nostalgia of a small in-group, and the inaccessibility of a true appreciation of that unique nostalgia to those who were not part of that in-group while the memories were being made; the third, and one might fairly guess any potential future seasons, considers this fixation in closer detail, and provides a new vantage point for the viewer to observe from - two self-inserts in as-yet-undeveloped characters who are just as outside of the Hidamari in-group for the time being.