From the moment that Made in Abyss introduces Riko, it shows her as a headstrong, ebullient, and curious young girl. Her initial conversation with fellow red whistle, Nat, establishes their dynamic — Riko, the curious one who hordes valuable relics and thinks too far ahead of where she’s at, Nat, the one who cares about her but hides it under a layer of bluster.
The problem Riko runs into while excavating isn’t that she’s incapable of finding things but that she finds so many relics, it’s difficult for her to carry them all in her backpack. She acts instantly when Nat is in trouble, getting herself in trouble in the process.
No sooner has she been rescued by a strange light than Riko stumbles upon a prone body. When she prepares to resuscitate him, Riko discovers that not only is he not breathing, he’s also not human. Rather than reacting surprised, scared, or shocked, she’s enchanted. Riko immediately begins poking and prodding him, taking in a more detailed snapshot of his appearance, once she realizes that he’s not dead. Then, naturally, she hauls him behind her as well, another relic for her collection.
At about the halfway point of the series, I began to realize that Riko wasn’t exactly a popular character. One subsection of viewers didn’t appreciate Reg taking more of the spotlight, especially once Riko became incapacitated and Nanachi took up her role of explaining details of the abyss to Reg — made all the more jarring since Made in Abyss began as an almost by-the-numbers monomyth narrative for Riko. Another set of viewers disliked her carefree attitude.
I never understood why Riko’s was personality was so often boiled down to “cute, happy girl who likes to cook,” since I thought her character was one of a curious scientist from the beginning. Riko is a bit of a rare character, and one that I’d actually like to see in anime more frequently. All-too-often, characters with the same buoyant personality are also presented as stupid — with the foil portrayed as an intelligent too-serious type — but Riko eschews this when she steps onscreen. She isn’t stupid. She’s infinitely curious about the world around her, leading to an encyclopedic knowledge of the Abyss, from what she’s been taught in school to her own research.
Riko’s curiosity is certainly a double-edged sword. The one episode where she’s left alone, she soon finds trouble which she then has to fight her way out of, nearly dying in the process until Reg revives. That same curiosity can be mistaken for stupidity or pure emotional response. I see Riko as someone who actually struggles sometimes to empathize with people — or at least see how her invasive approach to things driven by curiosity can stomp on the emotions of others involved.
Most importantly, this makes Riko an invaluable partner for Reg, who has the physical strength that Riko doesn’t but lacks her cool head under pressure and knowledge of the Abyss. Reg loses his head often in high-pressure situations, especially without Riko (later Nanachi) able to feed him information or instructions. Not only can Riko provide instruction to Reg, but she handles pressure well — even as she was succumbing to the fourth-layer curse she was telling Reg how to save her life — and her effervescent attitude towards discovery and life drags a character like Reg out of his own head for a change.
When faced with horror after horror in the Abyss, a personality like Riko’s is invaluable (for another example, see Yuki Takeya’s role in School-Live!). This is also why her encounter with the departing Mitty is so important, and could give hints to how Riko will fit in their new dynamic as a trio: she keeps them moving forward.