Slice-of-life Japanese anime is all about the familiar everyday adventures of real life, so the protagonists often feel down-to-earth compared to magical girls or shonen action leads. There's no single right way to design and write a slice-of-life anime protagonist. However, in the wake of so many generic self-insert characters, some audiences feel frustrated with these characters and long for a better-defined, more badass lead.
Slice-of-life has a reputation for being an easygoing, casual subgenre with gentle and vaguely defined self-insert protagonists to match. While there will always be an audience for that, it makes true badass slice-of-life protagonists stand out all the more, and that's what slice-of-life needs. Best of all, these badass SOL leads follow the key rules for protagonist design, regardless of genre.
Badass Slice-Of-Life Protagonists Have Better Writing
Badass slice-of-life protagonists, rare as they are, have much better writing than generic, self-insert protagonists do. It's a near-universal rule that protagonists in fiction must play an active role in the story, and they can't be passive for long, if at all. Any story's protagonist must earn their role as the central character by getting things done. In the easygoing context of slice-of-life anime, that calls for a real badass. Such characters have clearly defined interests, goals, and skills — behaving more like a shonen action star in an everyday setting. Strongly and clearly written characters will naturally become compelling and memorable, since they actually stand for something and draw viewers in.
These active protagonists have sympathetic flaws and room for growth, which are essential for any character's personal arc. Self-insert protagonists certainly have flaws too — such as being too shy to talk or feeling lonely without friends — but those characters rarely do anything about it. Instead, a badass slice-of-life protagonist has the courage to face their own flaws or obstacles. They made every effort to overcome them, one personal fight at a time. It's inspiring to watch a badass protagonist bravely face their internal and external demons. By contrast, a passive, generic protagonist often needs someone else to help them. There's nothing inspiring about that, even if it flatters the supporting character.
Self-Insert Protagonists Are Undefined & Lack Growth
Generic and self-insert characters like Junta Shiraishi in Kubo Won't Let Me Be Invisible and Ayumu Tanaka in When Will Ayumu Make His Move? lack the strong writing of their badass counterparts. By design, these characters are meant to be relatable to absolutely everyone in the target audience, which paradoxically makes them no one at all. These self-inserts are the opposite of a traditional fiction protagonist. They possess weak or nonexistent character arcs, undergo minimal change, lack a substantial goal, and remain too passive in their everyday lives. Clearly, the idea is to make them go with the flow as everyday life happens to them, but deep down, anime fans know that passive, unmotivated heroes are the most boring kind.
Junta Shiraishi is the inverse of a compelling badass MC who gets things done. Junta exists just to put audiences in his shoes and let everyday life happen around him, and his character is little more than an excuse to get the plot started. Junta has a generic appearance and personality, doesn't have clearly defined goals, has no special skills or interests, and relies on the lovable co-star Nagisa Kubo to make his life interesting. That doesn't make Junta repulsive to anime fans, but it shows how disappointing self-inserts like him can be. It also lowers the bar for SOL protagonists.
By trying to make self-inserts like Junta ultra-relatable and sympathetic, they don't have enough depth to undergo true character growth. Instead, much of their growth is external. Characters like Junta Shiraishi and Ayumu Tanaka might change their social life for the better when their love interest makes a move or their classmates befriend them. A true badass MC will actively change themselves for the better and reshape the world around them. A clearly defined character knows how to make those changes. An ill-defined, non-badass character like Junta doesn't really know who he is or what he stands for. No one like that can change the people or world around them; they need everyone else to change them instead. Passive characters like those aren't compelling.
Badass Protagonists Balance Strength With Weakness
Badass and self-insert protagonists alike have sympathetic flaws in slice-of-life anime, and in the course of their everyday lives, those flaws will be addressed. All that makes for a relatable narrative in a familiar slice-of-life setting. However, badass MCs have strengths to balance those flaws and personal demons, which makes them better-rounded characters. Whether a character is all strength or all weakness, they're become a flat character defined by just one trait. A badass has every ingredient for a good character arc. They have flaws or problems to address, but also have the strength and clearly defined motivations needed to overcome them.
A good example is Shikimori from the Shikimori's Not Just a Cutie anime series. While her dandere boyfriend Izumi is a self-insert, Shikimori herself is clearly defined by her athletic prowess, good grades at school, assertive personality, and her protective ways. These make her an excellent partner and certainly a badass main character. Shikimori seemed perfect at first, but this pink-haired badass also had personal flaws such as a jealous streak and insecurities about being a younger sister while her much older brother was so cool. This balanced Shikimori's character and made her strength as a badass more meaningful. Unlike self-inserts, Shikimori's fully equipped to face her faults, change the people around her, and improve herself as she sees fit.
Tomo Aizawa in Tomo-Chan is a Girl! is like that too. She's a clearly defined badass MC, an excellent karate practitioner, and has energetic confidence in herself. Additionally, she secretly worries she's not outwardly girly enough for her crush and childhood friend, Jun, to love her back. Tomo assumes an active role in all this and explores herself as a person, striving to balance her authentic adventurous side with her sympathetic desire to appeal to Jun as a lovestruck maiden. It's not easy, and even felt scary or hopeless at times. But as a badass slice-of-life protagonist, Tomo proactively fought hard to succeed — making her truly inspiring and relatable.